Lesson 15: Antibodies. Immunity Tests: Test of neutralization Toxin Action By Antitoxin, Precipitation Test, Agglutination Test

Question 1

What tissue does human organism’s immune system consist of?

Answer 1

Immune system is the complex of organs, tissues and cells providing genetic constancy of
organism.

The material base of immune system is the complex of lymphoid organs, which are organized tissue containing large numbers of lymphocytes in a framework of non-lymphoid cells.

In these organs, the interaction of lymphocytes make with non-lymphoid cells are important to lymphocyte development.

This interaction initiates adaptive immune responses, surviving and maintenance of lymphoid organs.

Question 2

Name the central and peripheral organs of human immune system and their functions .

Answer 2

The lymphoid organs are divided into central or primary lymphoid organs, and peripheral or
secondary lymphoid organs.

Primary lymphoid organs are places where lymphocytes are generated.

Peripheral or secondary lymphoid organs are places where adaptive immune response are initiated and lymphocytes are maintained.

The central lymphoid organs include bone marrow and thymus.

The peripheral lymphoid organs are lymph nodes, spleen, and lymphoid tissues associated with mucosa, like the gut-associated with tonsils, appendix and bronchial linings.

Question 3

Describe the process of humoral and cellular immune response development

Answer 3

The humoral and cellular immune responses are two critical components of the immune system that work together to identify and eliminate pathogens and other substances that can harm the body. Here is a brief overview of the processes involved in the development of these immune responses:

Humoral Immune Response:
1. Exposure to an antigen: An antigen is any substance that can trigger an immune response. When a pathogen or foreign substance enters the body, specialized cells called B-cells detect it.
2. Activation and differentiation of B-cells: When a B-cell detects an antigen, it becomes activated and starts to divide rapidly. Some of these B-cells become plasma cells, which produce and secrete large amounts of antibodies specific to the antigen.
3. Production of antibodies: Antibodies are proteins that recognize and bind to the specific antigen that triggered the immune response. The antibodies circulate in the bloodstream and can help to neutralize the pathogen or foreign substance and stimulate other cells to destroy it.
4. Memory B-cells: After an infection is cleared, a small proportion of B-cells remain as long-lived memory cells that can quickly recognize the same antigen and mount a rapid immune response if re-exposed.

Cellular Immune Response:
1. Recognition of antigens: When a pathogen or infected cells are detected, specialized cells in the immune system called T-cells detect and recognize the antigens.
2. Activation and differentiation of T-cells: When a T-cell recognizes an antigen, it becomes activated. Some of these T-cells become helper T-cells that stimulate and activate other immune cells such as cytotoxic T-cells and macrophages.
3. Cytotoxic T-cells: Cytotoxic T-cells directly attack and destroy infected cells that are displaying the antigen on their surface. The cytotoxic T-cells kill infected cells by releasing substances that cause the death of the cell.
4. Memory T-cells: After an infection is cleared, a small proportion of T-cells remain as long-lived memory cells that can quickly recognize the same antigen and mount a rapid immune response if re-exposed.

Both the humoral and cellular immune responses work together to provide protection against pathogens and other harmful substances. The humoral response is more effective against pathogens in bodily fluids, such as bacteria, while the cellular response is more effective against intracellular pathogens such as viruses.

Question 4

Name the classes of lymphocytes

Answer 4

T-cells
Th (helper) cells, or CD4 cells Provide “help” or the possibility of
manifestation of immune functions by
other lymphocytes
TS(suppressor) cells or CD8 cells Inhibit other manifestations of immune
functions lymphocytes
Tc (cytotoxic) cells or CD8 cells Cause cytolysis and death of “target
cells”
TD or TDTH (delayed type
hypersensitivity) cells or CD4 cells
“Recruit” and regulate different
nonspecific blood cells and macrophages
to provide delayed-type hypersensitivity
reactions (Type IV)
B-cells
B lymphocytes “Precursors” of antibody-producing cells
Plasma cells Mature, active antibody-producing cells
Unclassified cells
Natural killer Cause cytolysis and death of “target
cells”

Question 5

Name the cells phagocyting antigens

Answer 5

The cells that phagocytose (ingest) antigens are called phagocytes. The following are examples of phagocytic cells:

1. Neutrophils: These are the most abundant type of white blood cells and are the first responders to an infection.
2. Monocytes/Macrophages: Monocytes are produced in the bone marrow and are released into the bloodstream. Once in the tissue, they differentiate into macrophages and play a critical role in eliminating pathogens and debris.
3. Dendritic cells: These cells are found in tissues that interface with the external environment, such as the skin, respiratory tract, and gut. They function primarily as antigen-presenting cells, and once they contact an antigen, they migrate to lymph nodes to trigger the immune response.
4. Eosinophils: These cells are primarily involved in parasitic infections and play a role in allergic reactions.
5. Basophils: These cells are the least abundant type of white blood cells and are often involved in allergic reactions.

Once these phagocytic cells contact an antigen, they engulf it and break it down into small pieces that can be presented to other immune cells. This presentation of antigens is a crucial step in activating and directing the immune response.

Question 6

Name the cells taking part in the process of antigen representation to T- and B- lymphocytes

Answer 6

All the cellular elements of blood, including cells of immune system, arise from pluripotent
hemopoietic stem cells located in the bone marrow. These pluripotent cells divide to produce two types
of stem cells: common lymphoid progenitor and common myeloid progenitor. Common lymphoid
progenitor gives rise to natural killer cells, T lymphocytes and B lymphocytes. Common myeloid
progenitor gives rise to different types of leukocytes, erythrocytes and megakaryocytes, that produce
platelets for blood clotting.
T and B lymphocytes are distinguished by their sites of differentiation: the thymus and bone
marrow. Mature T and B lymphocytes circulate between blood and peripheral lymphoid tissue. After
encounter with antigen, B cells differentiate into antibodies-producing plasma cells. T cells differentiate
into effector T cells with variety of functions. Natural killer cells lack antigen-speficity.

Question 7

Name the cells transforming and turning into plasmocytes, producing antibodies. Name the cells that stimulate this process

Answer 7

The cells that transform and turn into plasmocytes, producing antibodies, are B-cells. B-cells are a type of white blood cell that produces and secretes antibodies into the bloodstream. When a B-cell recognizes a specific antigen, it undergoes a transformation and starts dividing rapidly. Some B-cells differentiate into memory B-cells for long-term protection, and others become plasmocytes that produce and secrete large quantities of antibodies specific to the recognized antigen. These antibodies circulate in the bloodstream and can bind to the antigens, neutralizing or helping to eliminate the pathogen or foreign substance.

The cells that stimulate the transformation of B cells into plasmocytes and the production of antibodies are helper T-cells. Helper T-cells are a type of white blood cell that plays a critical role in the immune response. When a helper T-cell recognizes an antigen presented by an antigen-presenting cell, it releases cytokines that activate and transform B cells into plasmocytes. The cytokines released by helper T-cells also enhance the antibody response and stimulate the proliferation and differentiation of other immune cells involved in the immune response. Therefore, helper T-cells play a crucial role in coordinating and regulating the immune response against pathogens and other foreign substances.

Question 8

Name the cells suppressing the immune response.

Answer 8

There are several types of cells that suppress the immune response. Here are a few examples:

1. Regulatory T-cells: These specialize in suppressing excessive immune responses to self-antigens and preventing autoimmune diseases.
2. Myeloid-derived suppressor cells (MDSCs): These cells are produced during chronic or severe inflammation and can dampen the immune response.
3. B-cells: Certain subsets of B-cells can produce suppressive molecules that hinder the activity of other immune cells.
4. Natural killer T-cells (NKT cells): NKT cells can produce cytokines that suppress the immune response against cancer and infections.

The immune system has evolved several ways to regulate and modulate immune responses to prevent excessive inflammation, tissue damage, and autoimmune diseases. These cells play an essential role in maintaining a balanced immune response and preventing immune-mediated illnesses.

Question 9

Name the cells killing tumor cells and cells infected by viruses.

Answer 9

The cells that kill tumor cells and cells infected by viruses are called cytotoxic cells, which include:

1. Cytotoxic T-cells: These cells are also known as CD8+ T-cells and are critical in killing infected cells, tumor cells, and cells that display foreign antigens on their surface.
2. Natural killer (NK) cells: NK cells are large granular lymphocytes that can detect and kill infected or abnormal cells, including cancer cells. They do not require the antigen presentation and activation process of other immune cells.

Both cytotoxic T-cells and NK cells use a variety of mechanisms to kill target cells, including the release of cytotoxic enzymes and proteins to induce apoptosis (programmed cell death) of the target cells. Both are important in protecting the body against viral infections and cancer.

Question 10

Cytokines- definition and types

Answer 10

Cytokines are a broad and diverse group of small proteins that are secreted by cells of the immune system, as well as other cell types, in response to various stimuli. They play a critical role in cell signaling and communication, controlling the immune response, and mediating inflammation.

Some types of cytokines include:

1. Interleukins: These cytokines are involved in communication between leukocytes (white blood cells), regulating immunity, inflammation, and hematopoiesis (the formation and development of blood cells).
2. Tumor necrosis factor (TNF): TNF helps mediate inflammation, cell death, and immunity.
3. Interferons: Interferons are essential in antiviral defense and can also inhibit cell growth and proliferation.
4. Chemokines: Chemokines are a type of cytokine that helps guide immune cells to areas of infection or inflammation.
5. Growth factors: Growth factors stimulate the growth, proliferation, and differentiation of cells, including blood cells, immune cells, and other cells and tissues in the body.
6. Transforming growth factor-beta (TGF-β): TGF-β plays a role in cellular growth and differentiation, wound healing, and immune regulation.

Cytokines are involved in a diverse range of biological processes and functions, including immune response, inflammation, cell growth, differentiation, and tissue repair and regeneration. They are particularly important in regulating the magnitude and duration of the immune response to pathogens, foreign substances, and damaged tissue.

Question 11

Antigens of main histocompatibility complex, their role in immune response development.

Answer 11

Antigens of the major histocompatibility complex (MHC) are a group of proteins expressed on the surface of almost all nucleated cells in the body. The MHC-encoded molecules, also known as human leukocyte antigens (HLA) in humans, are critical in the development of immune responses by alerting the immune system to the presence of foreign substances, such as pathogens or cancer cells.

The MHC is divided into two categories: MHC class I and MHC class II.

MHC class I molecules are expressed on almost all nucleated cells in the body. They present processed antigenic peptides from intracellular pathogens or damaged self-cells to CD8+ T-cells (cytotoxic T-cells). CD8+ T-cells recognize the MHC class I-bound peptide and become activated to kill the cells presenting the foreign peptide, thus eliminating the source of the antigen.

MHC class II molecules are expressed on specialized antigen-presenting cells such as dendritic cells, macrophages, and B-cells. They present processed antigenic peptides from extracellular pathogens to CD4+ T-cells (helper T-cells). CD4+ T-cells recognize the MHC class II-bound peptide and become activated to help B-cells produce antibodies against the pathogen.

The MHC is highly polymorphic, meaning that there are many different versions or alleles of MHC genes within a population. This diversity is necessary for the immune system to be able to recognize a wide range of possible antigens. MHC compatibility is essential for successful transplantation because the immune system can recognize foreign MHC molecules as non-self and mount an immune response against them.

Therefore, the role of MHC in immune response development is critical because it allows the immune system to distinguish between self and non-self cells and provides the necessary signals for activating immune cells to destroy infectious agents.

Question 12

MHC classes and their characteristics.

Answer 12

There are two classes of major histocompatibility complex (MHC) molecules, namely MHC class I and MHC class II, which differ from each other in their structure, tissue distribution, and functions.

MHC class I molecules:

1. Structure: MHC class I molecules consist of a transmembrane heavy chain and a small protein called beta-2 microglobulin. The heavy chain has three extracellular domains, with the peptide-binding groove situated between the first and second domains.
2. Tissue distribution: MHC class I molecules are expressed on almost all nucleated cells in the body, where they present processed antigenic peptides from endogenous sources, such as intracellular pathogens or damaged self-cells.
3. Function: MHC class I molecules present antigenic peptides to CD8+ T-cells (cytotoxic T-cells) and activate them to kill the cells displaying the foreign peptides, thus eliminating the source of the antigen.

MHC class II molecules:

1. Structure: MHC class II molecules consist of two transmembrane chains, alpha and beta, each with two extracellular domains. The peptide-binding groove is situated between the alpha and beta chains.
2. Tissue distribution: MHC class II molecules are expressed on specialized antigen-presenting cells such as dendritic cells, macrophages, and B-cells, where they present processed antigenic peptides from exogenous sources, such as extracellular pathogens.
3. Function: MHC class II molecules present antigenic peptides to CD4+ T-cells (helper T-cells) and activate them to help B-cells produce antibodies against the pathogen.

Both MHC class I and II molecules are highly polymorphic, meaning that there are several different versions (alleles) of MHC genes within a population. This diversity is necessary for the immune system to be able to recognize a wide range of possible antigens. MHC compatibility is essential for successful transplantation because the immune system can recognize foreign MHC molecules as non-self and mount an immune response against them.

Question 13

Antibodies, definition and main properties

Answer 13

Antibodies, also known as immunoglobulins (Ig), are Y-shaped proteins produced by B-cells and plasma cells as a part of the adaptive immune response against a specific antigen or pathogen. Antibodies play a critical role in defense against infectious agents and can also contribute to the protection against cancer.

The main properties of antibodies include:

1. Specificity: Antibodies bind to a specific antigen or pathogen through complementary antigen-binding sites on the tips of the Y-shaped molecules, enabling precise recognition and destruction of the target. Each antibody has a unique antigen-binding site that is specific for a particular antigen.
2. Diversity: The immune system can produce a practically infinite variety of different antibodies that can recognize and bind to different antigens. This diversity is generated by genetic recombination, somatic mutation, and other mechanisms.
3. Affinity: Antibodies recognize and bind to antigens with a high degree of selectivity, and their binding affinity increases with each successive interaction with the antigen. This enables antibodies to persistently neutralize and clear the target antigen from the body.
4. Opsonization: Antibodies can form a coat (a process called opsonization) around the target pathogen, making it more visible and easier for phagocytic cells to recognize and eliminate.
5. Complement activation: Antibodies can activate the complement system, which leads to the destruction of the pathogen by the formation of a membrane attack complex.
6. Isotype switching: B-cells can switch the isotype of the antibody produced from one subtype to another, depending on the type of pathogen encountered. Different isotypes have different effector functions (such as binding to different cells or activating different types of immune responses), thus enhancing the immune response and providing the appropriate response to different pathogens.

In summary, antibodies play a critical role in the adaptive immune response against pathogens and cancers. They recognize and bind specifically to their target antigen, generate diversity to enable recognition of a vast range of antigens, increase binding affinity with repeated interactions, opsonize the target, activate the complement system, and switch isotypes to provide the appropriate response to different types of pathogens.

Question 14

How is the immune serum obtained?

Answer 14

The immune serum, or antiserum, is obtained by immunizing an animal, such as a rabbit, mouse, or goat, with an antigen that is associated with a particular disease or pathogen. The animal is injected with the antigen or a related product, either in a purified or conjugated form, stimulating the animal’s immune system to produce antibodies against the antigen.

Once the animal has produced enough antibodies, the blood is collected, and the serum is separated from the other blood components. The serum contains the specific antibodies produced by the animal in response to the antigen, and it can be used to treat or diagnose the disease.

The procedure of obtaining the immune serum includes the following steps:

1. Immunization: The animal is immunized with the antigen of interest. This can be done by injection, ingestion, or other methods. The animal is injected with the antigen repeatedly, over a period of weeks or months, to stimulate the immune system to produce sufficient levels of specific antibodies.
2. Blood collection: Once the animal has produced enough antibodies, the blood is collected by venipuncture. This process is usually done under anesthesia, and the amount of blood collected is closely monitored to ensure the animal’s wellbeing.
3. Serum separation: The collected blood is centrifuged to separate the serum, containing the antibodies of interest, from other blood components such as cells and clotting factors.
4. Antibody purification: The serum is purified using techniques such as chromatography or affinity purification, to obtain a high concentration of the specific antibodies.

The obtained immune serum can be used in diagnostic tests, such as ELISA and Western blot, or for passive immunization in patients who have been exposed to the disease-causing antigen or pathogen. It can also be used to produce monoclonal antibodies or develop vaccines.

Question 15

How is the serum neutralizing tetanus toxin obtained?

Answer 15

The serum neutralizing tetanus toxin, also known as anti-tetanus antiserum, is obtained by immunizing an animal, usually a horse or a sheep, with tetanus toxoid. The toxoid is a modified and inactivated form of the tetanus toxin that is unable to cause disease but can still stimulate the immune system to produce antibodies against the toxin.

The procedure of obtaining anti-tetanus antiserum includes the following steps:

1. Immunization: The animal is immunized with tetanus toxoid, typically by subcutaneous injection. The first injection is usually followed by several booster doses over several weeks or months to stimulate the immune system to produce a high level of specific antibodies against the toxoid.
2. Blood collection: Once the animal has produced enough antibodies, the blood is collected by venipuncture. This process is usually done under anesthesia, and the amount of blood collected is closely monitored to ensure the animal’s wellbeing.
3. Serum separation: The collected blood is centrifuged to separate the serum, containing the antibodies of interest, from other blood components such as cells and clotting factors.
4. Antibody purification: The serum is purified using techniques such as chromatography or affinity purification to obtain a high concentration of specific antibodies against the tetanus toxin.

The purified anti-tetanus antiserum is then tested for its effectiveness in neutralizing the tetanus toxin. This is typically done by mixing the antiserum with a sample of the tetanus toxin and measuring whether the toxin is still able to cause harm to cells or animals. If the antiserum is effective in neutralizing the toxin, it can be used for passive immunization in individuals who have been exposed to the tetanus toxin.

Question 16

What antigens induce the production of antitoxins, agglutinins, , precipitins, bacteriolysins, hemolysins, antilymphocytic antibodies?

Answer 16

The antigens that induce the production of antibodies can vary depending on the type of antibody. Here are some examples:

1. Antitoxins: Antitoxins are specific antibodies that can neutralize toxins produced by bacteria. They are produced in response to exposure to toxins such as tetanus toxin, diphtheria toxin, and botulinum toxin.
2. Agglutinins: Agglutinins are antibodies that can cause bacteria or red blood cells to clump together. They are produced in response to exposure to certain bacteria or viruses, such as Salmonella or E. coli.
3. Precipitins: Precipitins are antibodies that can cause the formation of a visible precipitate when they react with a soluble antigen. They are produced in response to exposure to soluble antigens, such as proteins from fungi, viruses, or bacteria.
4. Bacteriolysins: Bacteriolysins are antibodies that can destroy bacteria by causing the cell membrane to rupture. They are produced in response to exposure to specific bacteria, such as Streptococcus pneumoniae or Neisseria gonorrhoeae.
5. Hemolysins: Hemolysins are antibodies that can cause destruction of red blood cells. They are produced in response to exposure to certain bacteria or viruses, such as Streptococcus pyogenes or the Epstein-Barr virus.
6. Antilymphocytic antibodies: Antilymphocytic antibodies (ALA) are antibodies that target lymphocytes, a type of white blood cell involved in the immune response. They are typically produced in response to exposure to foreign lymphocytes, such as in blood transfusions or organ transplants.

In general, the immune system produces different types of antibodies in response to different types of foreign substances or organisms, known as antigens. The specific type of antibody produced depends on the nature of the antigen and the specific immune response required to neutralize or eliminate the threat.

Question 17

What antibodies develop in the organism if diphtheria toxoid is developed?

Answer 17

If a person is immunized with diphtheria toxoid, their immune system will produce antibodies against the diphtheria toxin. These antibodies are called antitoxins and are a type of immunoglobulin (IgG) produced by plasma cells.

The diphtheria toxoid vaccine contains a modified and inactivated form of the toxin, called toxoid, which is unable to cause disease but can still stimulate the immune system to produce a strong response. When the toxoid is injected into the body, the immune system recognizes it as a foreign invader and activates B cells to produce antibodies specific to the toxoid.

Over time, these B cells differentiate into long-lived plasma cells that continue to produce antibodies against the toxin. The antibodies are then circulated throughout the body, ready to neutralize any diphtheria toxin that enters the system.

The resulting antitoxin levels can provide protective immunity against diphtheria for many years. Booster doses of the vaccine are recommended to maintain optimal levels of protective immunity over time.

Question 18

What is an antibody titer?

Answer 18

An antibody titer is a measure of the concentration of antibodies in a person’s blood sample. It is commonly used to determine an individual’s immune response to a particular infectious agent or vaccine.

Antibody titers are determined by measuring the dilution at which antibodies can still be detected in a blood sample using a laboratory test, such as an enzyme-linked immunosorbent assay (ELISA) or a neutralization assay. The test measures the level of specific antibodies present in the blood sample and provides a quantitative measure of immunity to a particular infectious agent.

The result of an antibody titer is reported as a numerical value, indicating the dilution factor at which the antibodies are detected. For example, a titer result of 1:512 means that the antibodies were present at a detectable level at a dilution of 1 part blood to 512 parts diluent solution.

Antibody titers can be used to assess an individual’s immune status for a particular disease, to monitor the effectiveness of immunizations, or to determine if a person needs to receive a booster vaccine. High antibody titers indicate a robust immune response and protective immunity, while low titers may indicate a need for further immunization or a weakened immune response.

Question 19

Chemical nature of antibodies.

Answer 19

Antibodies, also called immunoglobulins (Ig), are glycoproteins that are produced by the immune system in response to foreign substances, such as bacteria, viruses, or toxins. They play a key role in defending the body against infections by recognizing and neutralizing or eliminating foreign invaders.

The chemical nature of antibodies is complex and diverse, depending on their type and function. However, all antibodies share a basic structure that includes four protein chains, two heavy chains and two light chains, that are connected by disulfide bonds to form a Y-shaped structure. Each chain consists of a series of repeating segments called domains that are responsible for the antibody’s binding and biological activity.

There are five types of heavy chains in antibodies, called IgM, IgG, IgA, IgD, or IgE, that differ in size, shape, and function. The heavy chains determine the class or isotype of the antibody, which influences its biological activity, distribution, and function. The two types of light chains are called kappa (κ) and lambda (λ) chains, which also affect the antibody’s specificity and biologic function.

The functional unit of the antibody is the Y-shaped molecule, with two identical antigen-binding fragments, or Fab regions, at the tips of the Y that recognize and bind to the specific antigen. The third region, called the Fc region, interacts with other components of the immune system to eliminate the antigen, such as activating complement proteins, binding to macrophages for phagocytosis, or recruiting other immune cells.

Antibodies are glycoproteins, meaning that they have complex sugar molecules attached to them. These sugar molecules, called glycans, are important for the stability and solubility of the antibody, as well as influencing its biological activity and immune function.

In summary, antibodies are complex and diverse proteins composed of heavy and light chains that interact with antigens through their Fab regions and interact with other immune cells and molecules through their Fc region. Antibodies are glycoproteins with complex sugar molecules attached to them that influence their stability, solubility, and immune function.

Question 20

What is an active center of immunoglobulin?

Answer 20

The active center of an immunoglobulin, also known as the antigen-binding site or paratope, is a specific region of the immunoglobulin molecule that binds to a specific part of an antigen. This region is formed by the variable regions of the heavy and light chains of the immunoglobulin, which contain specific sequences of amino acids that determine the antibody’s specificity and its ability to recognize and bind a specific antigen.

The active center of an immunoglobulin is composed of a three-dimensional structure with a pocket or groove that fits the shape of a specific antigenic determinant, also called an epitope. The shape and chemical properties of the amino acid residues in the paratope interact with the epitope, forming a lock-and-key mechanism that allows the immunoglobulin to selectively bind to a specific antigen.

The flexibility and diversity of the amino acid residues in the active center of immunoglobulins allow them to recognize a wide range of antigens with high specificity and affinity. The process of binding to an antigen triggers a series of events that lead to the neutralization or elimination of the antigen by the immune system, such as opsonization, phagocytosis, complement activation, or signaling to other immune cells.

In summary, the active center of immunoglobulins is a specific region of the antibody molecule that binds to a specific antigenic determinant or epitope, allowing the antibody to selectively recognize and neutralize or eliminate foreign substances. The paratope is composed of variable regions of the heavy and light chains with specific amino acid residues that determine the antibody’s specificity and affinity for a particular antigen.

Question 21

Enumerate immunoglobulin classes, their importance in the organism.

Answer 21

Immunoglobulins (Ig) are a group of proteins produced by the immune system in response to foreign invaders, such as bacteria, viruses, and other pathogens. There are five different classes of immunoglobulins, known as IgG, IgM, IgA, IgD, and IgE, each with distinct characteristics and functions.

1. IgG: IgG is the most abundant class of antibodies in the bloodstream, accounting for about 75% to 80% of circulating immunoglobulins. IgG is important for the long-term immunity against many pathogens, including viruses, bacteria, and toxins. It can cross the placenta and provide passive immunity to the fetus, and can also activate complement proteins to enhance the clearance of pathogens.
2. IgM: IgM is the first immunoglobulin produced in response to an infection, and is a pentamer composed of five identical monomers linked by a J chain. IgM is important for the primary immune response against many pathogens, and can also activate complement proteins.
3. IgA: IgA is found predominantly in mucosal secretions, such as saliva, tears, and breast milk, and protects against infections at mucosal surfaces. IgA is produced as a dimer composed of two monomers linked by a J chain, and can transport across epithelial cells to provide local protection.
4. IgD: IgD is found on the surface of B lymphocytes and is involved in B cell activation and maturation, but its exact function is not fully understood.
5. IgE: IgE is involved in allergic reactions and defense against parasites. IgE binds to the surface of mast cells and basophils, triggering the release of histamine and other mediators that cause allergic symptoms, such as sneezing, itching, and swelling.

In summary, immunoglobulin classes are important components of the immune system that contribute to the defense against a wide range of pathogens and foreign substances. Each class has distinct characteristics and functions that contribute to the immunity of the organism.

Question 22

Name the immunoglobulin able to pass through the placenta

Answer 22

The immunoglobulin that is able to pass through the placenta is IgG. IgG is the only class of immunoglobulin that is able to cross the placenta from the mother to the fetus, providing passive immunity to the infant. This transfer of IgG provides protection to the neonate during the first few months of life, until the infant’s own immune system is fully developed and able to produce its own immunoglobulins.

Question 23

What immunoglobulin structure is able to bind to the appropriate antigen?

Answer 23

The antigen-binding site or paratope is the immunoglobulin structure that is able to bind to the appropriate antigen. This region is located at the tips of the variable regions of the immunoglobulin heavy and light chains and is formed by specific sequences of amino acids that create a pocket or groove that fits the shape of a specific antigenic determinant, also known as an epitope. The specificity and affinity of the immunoglobulin for a particular antigen are determined by the chemical properties and arrangement of the amino acid residues in the paratope. Upon binding to an antigen, the immunoglobulin may trigger various mechanisms of immune defense to eliminate the foreign invader, such as opsonization, complement activation or recruitment of other immune cells.

Question 24

Dynamics of antibodies accumalation.

Answer 24

The dynamics of antibody accumulation in response to an infection or vaccination can be divided into several phases:

1. Lag Phase: The first few days after exposure to a pathogen or vaccine, no measurable antibodies are present in the blood. During this time, B cells are activated and undergo clonal expansion and differentiation into plasma cells that secrete immunoglobulins.
2. Log Phase or Exponential Phase: As the activated B cells differentiate into plasma cells, the production of antibodies increases rapidly and reaches a peak after about 1-2 weeks. During this phase, large amounts of IgM and later IgG are produced in response to the antigen.
3. Plateau Phase: After the peak level of antibodies is reached, the production of new antibodies slows down and reaches a steady state. The duration of the plateau phase depends on the type of antigen, and can last from weeks to months or even years.
4. Decline Phase: Over time, the concentration of antibodies gradually decreases due to the natural turnover of immunoglobulins and the elimination of the pathogen or vaccine antigen. However, the presence of memory B cells can provide a faster and stronger response upon re-exposure to the antigen.

Factors that affect the dynamics of antibody accumulation include the dose and route of exposure, the type of antigen and pathogen, the age and health status of the individual, and the presence of pre-existing immunity or vaccination. Understanding the dynamics of antibody accumulation is important in the development of effective strategies for preventing and treating infectious diseases, as well as for monitoring immune responses in clinical settings.

Question 25

Secondary immune response and its pecularities.

Answer 25

The secondary immune response is a type of immune response that occurs upon re-exposure to an antigen that the immune system has previously encountered. It is a faster, stronger, and more specific response than the primary immune response, and is characterized by several peculiarities:

1. Rapid onset: The secondary immune response is faster than the primary response and can occur within hours to days after re-exposure to the same antigen.
2. Higher antibody levels: The concentration of antibodies produced during a secondary immune response is much higher than that of the primary response, due to the presence of memory B cells that can quickly differentiate into plasma cells and produce large amounts of immunoglobulins.
3. More specific: The secondary immune response is more specific than the primary response, as the memory B cells have undergone affinity maturation and can produce antibodies with higher affinity and specificity to the antigen.
4. Longer-lasting: The secondary immune response can last longer than the primary response, due to the presence of long-lived memory B cells and memory T cells that can persist in the body for years or even decades.
5. Different antibody isotypes: The secondary immune response may produce different antibody isotypes than the primary response, depending on the type of antigen and the location of the infection. For example, the secondary response to a viral infection may produce more IgG than the primary response, while the secondary response to a mucosal infection may produce more IgA.

The pecularities of the secondary immune response make it an important component of the immune system’s defense against infectious agents, as well as the basis for vaccination strategies that aim to induce long-term protective immunity against specific pathogens.

Question 26

What are immune tests?

Answer 26

Immune tests are medical tests that measure the function, level, and activity of the immune system components, including antibodies, antigens, cytokines, complement proteins, and immune cells. These tests can provide important diagnostic and prognostic information about infectious, autoimmune, allergic, and immunodeficiency diseases, as well as the response to vaccination and therapy. Immune tests may be performed on blood, urine, saliva, cerebrospinal fluid, or other body fluids and tissues, and can be carried out in a laboratory or point-of-care setting.

Some common types of immune tests include:

1. Antibody tests: These tests detect the presence and amount of specific antibodies in the blood, which can indicate past or recent exposure to an infectious agent or vaccination.
2. Antigen tests: These tests detect the presence and amount of specific antigens in body fluids, which can indicate the active infection with a specific pathogen.
3. Cytokine tests: These tests measure the level of cytokines, which are signaling molecules produced by immune cells that regulate the immune response, inflammation, and tissue repair.
4. Flow cytometry: This test analyzes the properties of blood or tissue cells, including their size, shape, and surface markers, to identify and quantify different types of immune cells.
5. Complement tests: These tests measure the level and activity of complement proteins, which play a role in the immune response and inflammation.
6. Histocompatibility tests: These tests determine the compatibility of cells or tissues for transplantation by matching the human leukocyte antigens (HLAs) of the donor and recipient.

Immune tests are an important tool in the diagnosis, management, and prevention of various diseases and conditions, as well as the monitoring of immune system functioning in different populations, such as infants, elderly, or immunocompromised individuals.

Question 27

What is sensitivity and specificity of immune tests?

Answer 27

Sensitivity and specificity are two important statistical measures that are used to evaluate the accuracy and reliability of immune tests in detecting the presence or absence of a disease or condition.

Sensitivity refers to the proportion of individuals with the disease or condition who test positive for it, i.e., the ability of the test to detect true positive results. It is calculated as the number of true positives divided by the sum of true positives and false negatives, expressed as a percentage.

For example, if a test has a sensitivity of 90%, it means that 90% of individuals with the disease or condition will test positive, while 10% will test negative (false negatives).

Specificity, on the other hand, refers to the proportion of individuals without the disease or condition who test negative for it, i.e., the ability of the test to avoid false positive results. It is calculated as the number of true negatives divided by the sum of true negatives and false positives, expressed as a percentage.

For example, if a test has a specificity of 95%, it means that 95% of individuals without the disease or condition will test negative, while 5% will test positive (false positives).

In general, a good immune test should have high sensitivity and specificity values, indicating that it can accurately identify both true and false negative or positive results, respectively. However, in some cases, a tradeoff may occur between sensitivity and specificity, where increasing one may decrease the other, depending on the type of test and the population being tested. Therefore, it is important to use sensitivity and specificity values in conjunction with other measures, such as positive predictive value (PPV) and negative predictive value (NPV), to determine the overall usefulness and reliability of an immune test for a specific disease or condition.

Question 28

What immune tests occurs between toxins and antitoxins?

Answer 28

Toxins and antitoxins are two types of immunological substances that interact with each other in the body and can be measured by immune tests. Toxins are harmful substances produced by certain bacteria, viruses, or fungi that can damage tissues or organs and cause disease. Antitoxins, on the other hand, are antibodies produced by the immune system in response to toxins, which can neutralize or destroy them.

The most common immune tests that occur between toxins and antitoxins are toxin neutralization assays (TNAs) and toxin-binding inhibition assays (TBIAs), which can measure the ability of antitoxins to neutralize or bind to toxins.

In the TNA, a known amount of toxin is mixed with a dilution series of antitoxin, and the mixture is incubated with cells or animals that are susceptible to the toxin. The endpoint of the assay is the highest dilution of antitoxin that can prevent the characteristic effects of the toxin on the cells or animals, such as death, paralysis, or cytotoxicity. The higher the titer of antitoxin, the greater the ability to neutralize the toxin.

In the TBI, a known amount of toxin is mixed with a dilution series of antitoxin, and the mixture is incubated with an excess of labeled antibody or receptor that can bind to the toxin. The endpoint of the assay is the concentration of antitoxin that can inhibit a certain percentage of the binding of the labeled antibody or receptor to the toxin, as compared to a control without antitoxin. The higher the inhibition percentage, the greater the ability to bind to the toxin.

TNAs and TBIAs are important tests for diagnosing and monitoring diseases caused by toxins, such as tetanus, diphtheria, botulism, and snake bite envenomation, and for evaluating the efficacy of antitoxin therapies and vaccines.

Question 29

How is the biological activity of antitoxic sera determined?

Answer 29

The biological activity of antitoxic sera, which contain high amounts of specific antibodies against toxins, can be determined by several immunological assays that measure the ability of the sera to neutralize or bind to toxins. The most common assays are the toxin neutralization assay (TNA) and the toxin-binding inhibition assay (TBI), which are described below in more detail:

1. Toxin neutralization assay (TNA): In this assay, a known amount of toxin is mixed with a dilution series of antitoxic sera and incubated with cells or animals that are susceptible to the toxin. The endpoint of the assay is the highest dilution of antitoxic sera that can prevent the characteristic effects of the toxin on the cells or animals, such as death, paralysis, or cytotoxicity. The higher the titer of antitoxic sera, the greater the ability to neutralize the toxin and prevent its harmful effects.
2. Toxin-binding inhibition assay (TBI): In this assay, a known amount of toxin is mixed with a dilution series of antitoxic sera and incubated with an excess of labeled antibody or receptor that can bind to the toxin. The endpoint of the assay is the concentration of antitoxic sera that can inhibit a certain percentage of the binding of the labeled antibody or receptor to the toxin, as compared to a control without antitoxic sera. The higher the inhibition percentage, the greater the ability to bind to the toxin and prevent it from binding to its receptor on target cells.

Other assays that can be used to determine the biological activity of antitoxic sera include the enzyme-linked immunosorbent assay (ELISA), the immunoblotting assay, and the radioimmunoassay (RIA), which all rely on the specific binding of antibodies to antigens or toxins.

The results of these assays can provide valuable information about the potency, specificity, and efficacy of the antitoxic sera, and can be used to guide the diagnosis, treatment, and prevention of toxin-mediated diseases, such as tetanus, diphtheria, botulism, and snake envenomation.

Question 30

What units are antitoxic sera measured in?

Answer 30

Antitoxic sera, which are prepared from the blood of animals or humans immunized with toxins or toxoids, are measured in terms of their content of specific antibodies against the target toxin or toxoid. The most common unit of measurement for antitoxic sera is the International Unit (IU), which is defined as the amount of antitoxin that is required to neutralize or bind a standardized amount of toxin or toxoid in a given assay.

The IU is an arbitrary unit of measurement that is based on the potency of a reference antitoxic serum, which has been assigned a potency value by international or national regulatory agencies, such as the World Health Organization (WHO) or the United States Pharmacopeia (USP). The potency value of the reference serum is expressed in IU per milliliter (IU/mL) and is used to calibrate the potency of other antitoxic sera, which are then assigned a potency value based on their ability to neutralize or bind the same standardized amount of toxin or toxoid in the same assay.

For example, in the case of tetanus antitoxin, the reference serum is the International Standard for Tetanus Antitoxin, which has a potency of 1500 IU/mL. When a new batch of tetanus antitoxin is produced, it is tested in the TNA or TBI assay against a standardized amount of tetanus toxin or toxoid, and its potency is expressed in IU/mL based on the reciprocal of the dilution that gives a certain level of neutralization or binding. The potency of the new batch is then compared to the potency of the reference serum to ensure that it meets the minimum requirements for efficacy and safety.

Question 31

Agglutination test: What is agglutination, what is the nature of antigen, what are the names of antibodies; two test phases; techniques,control?

Answer 31

Agglutination is the clumping together of cells or particles in the presence of a specific antibody directed against their surface antigens. Antigens are molecules or substances on the surface of cells or particles that can stimulate an immune response by the production of specific antibodies by the host’s immune system. Agglutination tests rely on the ability of the antibodies to cross-link the antigen molecules and promote the formation of visible clumps or aggregates, which can be detected and measured by various methods.

In the agglutination test, the nature of the antigen and the specific antibody used depend on the purpose of the test. For example, in the blood typing test, the antigens are on the surface of red blood cells, and the antibodies are directed against the major blood group antigens, such as A, B, or Rh. In the microbial agglutination test, the antigens are on the surface of bacteria or other microorganisms, and the antibodies are specific for the microbial antigens.

The names of the antibodies used in the agglutination test depend on the type of antigen and the immune system response it elicits. Antibodies that agglutinate red blood cells are called agglutinins, while antibodies that agglutinate bacteria or other microorganisms are called agglutinins or antisera.

The agglutination test consists of two phases: the sensitization phase and the agglutination phase. In the sensitization phase, the antigen and the corresponding antibody are mixed together and allowed to interact, usually at room temperature for a certain period of time. In the agglutination phase, the antigen-antibody complex is exposed to a cross-linking agent or other reactive substance that promotes clumping or agglutination of the particles.

The techniques used in the agglutination test also depend on the nature of the antigen and antibody involved. The most common agglutination tests include the slide agglutination test, the tube agglutination test, the latex agglutination test, and the particle agglutination test, each with their specific variations and applications. Each type of test requires appropriate controls and quality assurance measures to ensure the accuracy and reproducibility of the results.

In the control phase of the agglutination test, several controls are typically used to monitor the specificity and sensitivity of the test, as well as to detect potential false positive or false negative results. These controls may include the use of negative controls, positive controls, and serial dilutions of the antigen or antibody to establish the minimum detectable concentration or titer. Other controls may include the use of control sera or reference standards, or the comparison of results obtained by different methods or laboratories.

Question 32

Slide agglutination test: required ingredients, its techniques; how does the positive test look like; what is the advantage when compared to tube agglutination test.

Answer 32

The slide agglutination test is an immunoassay technique used to detect the presence of antibodies or antigens in a sample that can agglutinate or clump together in the presence of a specific reagent. The ingredients required for the slide agglutination test include a microscope slide, a disposable plastic dropper, a specimen or reagent, and a suitable agglutinating agent such as saline or antiserum.

The technique for performing the slide agglutination test is as follows:

1. Arrange the microscope slide on a flat surface, prepare the sample or reagent, and label the slide with the appropriate identification information.
2. Mix a small amount of the sample or reagent with a drop of saline or antiserum on the microscope slide. Use a disposable dropper or pipette and mix thoroughly to ensure the reaction.
3. Rotate the slide gently, using a circular motion, for up to 2-3 minutes to allow the reaction to occur and the agglutination to be visible under the microscope.
4. Observe the slide under low and high magnification with a microscope, and document the results by taking photographs or notes.

If the test is positive, agglutination or clumping of cells or particles will be visible on the microscope slide, indicating the presence of the target antigen or antibody in the sample. Positive results are often graded as 1+, 2+, 3+, and 4+, depending on the size and number of aggregates visible under the microscope.

One advantage of the slide agglutination test over the tube agglutination test is that it can be performed quickly and with minimal equipment or training. The slide agglutination test can also be used to detect a wide range of antigens or antibodies, including those that are difficult to detect by other methods. Additionally, the slide agglutination test is less prone to false-negative results than the tube agglutination test.

Question 33

Tube agglutination test: required ingredients, its technique, required controls, checking the results.

Answer 33

The tube agglutination test is an immunoassay technique used to detect the presence of antibodies or antigens in a sample that can agglutinate or clump together in the presence of a specific reagent. This test is commonly used for blood typing, microbial identification, and other diagnostic purposes. The ingredients required for the tube agglutination test include a test tube, a disposable pipette or dropper, a specimen or reagent, and a suitable agglutinating agent such as saline or antiserum.

The technique for performing the tube agglutination test is as follows:

1. Arrange the test tube in a rack, prepare the sample or reagent, and label the test tube with the appropriate identification information.
2. Add a small amount of the sample or reagent to the test tube, using a disposable pipette or dropper, and mix thoroughly.
3. Add a small amount of the agglutinating agent to the test tube, using the same pipette or dropper, and mix gently by inverting the tube several times.
4. Incubate the test tube at room temperature or a suitable temperature for a specific period of time, depending on the antigen-antibody reaction.
5. Observe the test tube for agglutination or hemolysis, which may occur as a visible clumping of the particles or cells or a clearing of the media.

In addition to the steps above, several controls are typically used to monitor the specificity and sensitivity of the test, as well as to detect potential false positive or false negative results. These controls may include the use of negative controls, positive controls, and serial dilutions of the antigen or antibody to establish the minimum detectable concentration or titer. For example, a negative control should contain only the reagents without the sample or antigen, while a positive control should contain a known positive antigen or antibody.

To check the results of the tube agglutination test, the observation of agglutination or hemolysis should be compared to the control tubes and interpreted based on the reactions and the titers obtained. Positive results are often graded as 1+, 2+, 3+, and 4+, depending on the size and number of clumps formed or the degree of hemolysis observed. Specificity and sensitivity can be determined by varying the concentrations of the reagents or by using different agglutinating agents.

In summary, the tube agglutination test is a simple and reliable technique for detecting the presence of antibodies or antigens in a sample. It requires minimal equipment and training and can be easily adapted to different diagnostic applications. However, quality control measures and proper interpretation of the results are essential to ensure the reliability and validity of the test.

Question 34

Indirect (passive) hemagglutinition test; what is an antigen in this test, how is it obtained , the test mechanism.

Answer 34

The indirect hemagglutination test (IHA) is an immunological assay used for the detection of antibodies against a specific antigen using agglutination of red blood cells (RBCs). The antigen in an IHA is usually obtained by extracting a specific antigenic component from a microorganism, plant, or animal tissue by using various methods like chromatography, electrophoresis, precipitation, etc.

The antigen obtained is bound or adsorbed to the surface of RBCs, such as sheep, chicken, or human, which do not have naturally occurring ABO or Rh antigens, and then used as a reagent for the IHA test. The test mechanism works as follows:

1. The specific antigen-coated RBCs are suspended in a diluent or buffer solution in test tubes. The test tubes may contain different dilutions of the antigen-coated RBCs, and it may or may not contain the serum sample of the patient.
2. If the patient’s serum contains antibodies against the antigen, the antibodies will bind to the antigen-coated RBCs and cause them to agglutinate or clump together, forming a visible precipitate. If the serum does not contain antibodies against the antigen, then no RBC agglutination occurs, resulting in a negative result.
3. The degree of agglutination or the appearance of the precipitate is generally graded from 0 to 4+ based on the concentration of antibodies present in the serum.

The IHA test is a quantitative test, and the results can be used to determine the antibody titer, which reflects the number of antibodies present in the serum. The IHA test is useful for diagnosing infectious diseases caused by bacteria, viruses, fungi, and parasites, as well as autoimmune diseases and allergies. The IHA test is a simple and sensitive serological method. It has the advantage of being relatively easy to perform and can be used as a screening test for a range of infectious diseases.

Question 35

Reverse indirect agglutination test; what is an antigen in this test, how is it obtained; the test mechanism.

Answer 35

The reverse indirect agglutination test (RIAT) is an immunological test used to detect the presence of specific antibodies in a patient’s serum against an antigen that has been bound to small particles, such as latex beads. This test is commonly used to diagnose infectious diseases caused by bacterial or viral agents.

In the RIAT, the antigen is the target of the test, and it is obtained from the pathogen responsible for causing the infection. The antigen is first extracted from the pathogen, purified, and then coated onto small particles, such as latex beads.

The test mechanism for the RIAT is as follows:

1. A small amount of serum from the patient is mixed with a suspension of the antigen-coated latex beads.
2. If the serum contains antibodies that are specific to the antigen, then the antibodies will bind to the antigen-coated latex beads, causing them to agglutinate or clump together.
3. The clumping of the latex beads can be visualized macroscopically or microscopically. The degree of agglutination can be graded based on the size and number of latex bead clumps, with 4+ representing the highest degree of agglutination.

The RIAT has several advantages over other serological tests. It is rapid, easy to perform, and sensitive, allowing for the detection of low levels of antibodies in patient serum. It is also relatively specific, as the antigen coating on the latex beads can be chosen to be highly specific to the pathogen of interest. Moreover, the RIAT does not require the use of specialized equipment, and the results can be read visually, making it a convenient diagnostic tool in resource-limited areas.

In summary, the RIAT is an effective diagnostic test that uses latex beads coated with an antigen to detect specific antibodies in a patient serum. It is a simple, rapid, and sensitive test suitable for the detection of infectious diseases caused by bacterial or viral agents.

Question 36

What is an antigen erythrocyte diagnosticum?

Answer 36

Antigen erythrocyte diagnosticum (AED) is a diagnostic reagent that is used to detect the presence of antibodies in serum against red blood cell antigens. Red blood cell antigens are proteins that are present on the surface of red blood cells and can trigger the immune system to produce antibodies against them.

AED contains a standardized suspension of red blood cells from different blood groups, which have been treated to ensure that they are free from contaminants that could interfere with the test. The red blood cells in the AED reagent are coated with antibodies against specific antigens, such as A, B, D, and Rh.

The AED reagent is used in serological tests, such as the direct and indirect Coombs tests, which are used to detect the presence of antibodies against red blood cell antigens. In the direct Coombs test, AED is mixed with the patient’s red blood cells, and the presence of agglutination indicates the presence of antibodies coated on the patient’s red blood cells. In the indirect Coombs test, AED is used to detect the presence of antibodies in the patient’s serum, which are then used to identify potential blood transfusion complications, such as hemolytic disease of the newborn.

In summary, AED is a diagnostic reagent used to detect the presence of antibodies in serum against red blood cell antigens. It contains a standardized suspension of red blood cells from different blood groups that have been treated to ensure that they are free from contaminants that could interfere with the test. AED is an essential tool in serological testing, especially in blood typing and compatibility testing.

Question 37

What is an antibody erythrocyte diagnosticum?

Answer 37

An antibody erythrocyte diagnosticum (Anti-Erythrocyte Diagnosticum or AEDC) is a diagnostic reagent that is used to detect the presence of antigens on the surface of red blood cells using antibodies against those antigens. These antibodies are obtained from an animal that has been immunized with the red blood cells from an animal of a particular species.

The antibody erythrocyte diagnosticum reagent contains a suspension of standardized red blood cells from a particular animal species, which have been treated to ensure that they are free from contaminants that might interfere with the test. Each suspension is coated with specific antibodies that are designed to detect red blood cell antigens that are of clinical relevance. Examples of such antigens are A and B blood group antigens.

The AEDC reagent is used in serological tests, such as the Coombs test, to detect the presence of antibodies against red blood cell antigens. In the Coombs test, the AEDC reagent is mixed with patient serum or red blood cells, and the presence of agglutination or clumping indicates the presence of antibodies coated on the red blood cells that have reacted with the antibodies in the AEDC reagent. This testing can provide information that is important in the diagnosis, prognosis, and treatment of diseases, such as hemolytic anemia.

In summary, the antibody erythrocyte diagnosticum is a diagnostic reagent that detects the presence of red blood cells antigens using antibodies against those antigens. It contains a standardised suspension of red blood cells from an animal species, which have been treated to remove contaminants, and is used in serological tests to detect antibodies against red blood cell antigens. The AEDC reagent plays an essential role in serological testing for diagnosing a range of clinical conditions, as well as for blood typing, compatibility testing, and transfusion medicine.

Question 38

Test techniques

Answer 38

There are numerous test techniques available, ranging from clinical laboratory techniques to point-of-care diagnostic tests. Here are some commonly used techniques:

1. Enzyme-Linked Immunosorbent Assay (ELISA): This is an immunological assay technique that uses antibodies and detects proteins (or antigens) in solution. ELISA is used to detect specific antibodies or antigens in the blood or other bodily fluids, making it a valuable tool in diagnosing infectious diseases and other conditions.
2. Polymerase Chain Reaction (PCR): PCR is a technique used to amplify DNA sequences. It is used in a variety of applications, such as identifying specific genetic markers in DNA samples, identifying infectious agents or genetic mutations, and diagnosing genetic disorders.
3. Western Blotting: Western blotting is a technique used to detect specific proteins in a sample. It involves the transfer of proteins from a gel to a membrane, where the proteins are then detected using specialized antibodies.
4. Fluorescence-Activated Cell Sorting (FACS): This is a technique that sorts cells based on their fluorescence properties. Cells are stained with fluorescent dyes or antibodies that target specific cell markers, and these cells are then sorted based on their fluorescence using a specialized machine.
5. Immunohistochemistry (IHC): IHC is a technique used to detect specific proteins in tissue samples. It involves staining tissue sections with antibodies that bind to a specific protein of interest, and then using specialized imaging techniques to visualize the stained proteins.
6. Electrocardiography (ECG): ECG is a technique used to record or monitor the electrical activity of the heart. It is often used to diagnose heart conditions, such as arrhythmias or heart attacks.
7. Radiography: Radiography is a technique used to create images of internal structures in the body, such as bones or organs. It involves exposing the body to ionizing radiation and capturing the resulting images using specialized equipment.
8. Point-of-care diagnostic tests: These are diagnostic tests that can be performed at the point of care, such as in a doctor’s office or clinic. Examples of point-of-care tests include rapid diagnostic tests for infectious diseases, such as strep throat or influenza, or home pregnancy tests.

These are just a few examples of the many test techniques used in healthcare and diagnostics today. The selection of the appropriate testing method largely depends on the medical condition and the specific diagnostic needs of the patient.

Question 39

Co-agglutination test

Answer 39

Co-agglutination test is a diagnostic serological test used to detect specific bacterial or viral antigens, toxins and antibodies. It is an adaptation of the enzyme-linked immunosorbent assay (ELISA) technique, where antibodies are adsorbed onto starch particles, and later co-aggregated with the bacterial antigens.

In the co-agglutination test, antibodies are first bound to particles coated with a natural polysaccharide such as Sepharose or Staphylococcus aureus, by adsorption process. These particles stimulate the activation of complement system, which leads to a precipitation reaction. Then, the target antigens present in patient’s serum or other biological fluids are allowed to react with these particles’ bound antibodies. The biotype of the bacterial species to be tested drives the choice of antibodies or polysaccharide coated particles.

If the target antigen is present in the patient’s sample, it will bind to the antibodies on the surface of the particles, causing the agglutination of bacteria or virus. This reaction involves the formation of visible clumps that can be detected under a microscope or by visual inspection. The degree of agglutination can be correlated with the antibody titer, enabling medical professionals to diagnose various infections including pneumonia, meningitis, and urinary tract infections and therefore be able to offer suitable antibiotics.

One of the advantages of the co-agglutination test is that it does not require labeled antibodies or other specialized reagents, making it a relatively simple and cost-effective diagnostic tool. However, the test has some limitations. The specificity may vary depending on the type of bacteria involved, and the sensitivity of the co-agglutination test is usually lower compared to other serological tests like ELISA and PCR. Additionally, variation from batch to batch and among different labs can occur, which necessitates a careful standardization and QC checks. Nonetheless, the co-agglutination test remains a useful tool for diagnosing bacterial and viral infections, especially in resource-limited settings.

Question 40

Agglutinating sera: what do they contain; how are they obtained: what are they used for?

Answer 40

Agglutinating sera are a type of polyclonal antibodies that contain high levels of specific antibodies against bacterial or viral pathogens. These antibodies are produced by the immune system in response to an infection or vaccination.

Agglutinating sera are obtained by injecting an animal with the specific pathogen or antigen of interest, which stimulates the production of specific antibodies. The animal’s serum is then collected to obtain the agglutinating sera, which is rich in specific antibodies against the pathogen.

Agglutinating sera is used for serological tests to detect bacterial or viral infections by agglutination. Agglutinating sera can also be used to identify the specific serotype or strain of a pathogen.

The agglutination assay involves mixing the pathogen or antigen with the agglutinating sera and observing the degree of clumping or agglutination that occurs. If the pathogen or antigen is present, the specific antibodies in the agglutinating sera will bind to it and cause agglutination, which can be visually detected.

Agglutinating sera can be used for several infectious agents, and the specificity and sensitivity of the test depend on the quality of the sera and the nature of the pathogen or antigen. Some examples of agglutinating sera include:

1. Salmonella agglutinating sera: used to identify the serotype or strain of Salmonella, which is important for disease surveillance and outbreak investigations.
2. Streptococcus agglutinating sera: used to diagnose streptococcal infections and to identify the specific serotype or strain responsible for the infection.
3. Escherichia coli agglutinating sera: used to identify different O serotypes of E. coli, which are associated with different diseases.
4. Influenza virus agglutinating sera: used to identify the serotype or strain of influenza virus responsible for the infection.

In summary, agglutinating sera are polyclonal antibodies used to detect specific pathogens or antigens and remain a valuable and commonly used tool for serological diagnosis of infectious diseases.

Question 41

What is the titer of the agglutinating serum?

Answer 41

The titer of an agglutinating serum is a measure of the concentration of specific antibodies against a pathogen or antigen. It indicates the highest dilution of the serum that still causes agglutination of the pathogen or antigen.

The titer of an agglutinating serum is usually determined by serially diluting the serum and mixing each dilution with a fixed amount of the pathogen or antigen. The mixture is then observed for agglutination, and the highest dilution that causes agglutination is considered to be the titer.

For example, if a serum sample is serially diluted by a factor of two, starting at a dilution of 1:10, and the highest dilution that still causes agglutination is 1:320, then the titer of the serum is 320.

The titer of an agglutinating serum is an important parameter for diagnosing infectious diseases and monitoring the progress of vaccination. A high titer indicates a high concentration of specific antibodies, which is typically associated with effective immunity against the pathogen. Conversely, a low titer may indicate insufficient immune response, which may require further evaluation or booster vaccination.

It is worth noting that the interpretation of agglutination titers is often pathogen-specific and requires reference to established guidelines or protocols specific to each pathogen.

Question 42

What are the differences between polyvalent and monovalent(monoreceptor) agglutinating sera?

Answer 42

Polyvalent and monovalent (monoreceptor) agglutinating sera are two types of sera used to detect antibodies against microorganisms. The key differences between the two are described below:

1. Specificity: Polyvalent sera contain antibodies against multiple strains or serotypes of a microorganism, while monovalent sera contain antibodies against a single strain or serotype. In other words, polyvalent sera are effective against a broader spectrum of microorganisms compared to monovalent sera.
2. Production: Polyvalent sera are produced by injecting animals with a mixture of strains or serotypes of a microorganism, while monovalent sera are produced by injecting animals with a single strain or serotype.
3. Applications: Polyvalent sera are used for broad-based serological testing, such as screening large populations for antibodies against several different strains or serotypes of a microorganism. They are also used for serotyping, to identify the specific strain or serotype causing an infection. In contrast, monovalent sera are used for in-depth studies of individual antigenic determinants or epitopes, which are critical in identifying subtle differences between strains or serotypes.
4. Sensitivity: Monoreceptor (monovalent) sera may have an increased sensitivity to antigens due to the absence of competing antibodies present in the polyvalent antibodies mixture. This can result in the detection of low antibody titers. However, monovalent sera may not detect all serotypes or strains of a microorganism, while polyvalent sera can cover most serotypes, especially if the formulation has been carefully produced.
5. Cost and availability: Polyvalent sera are generally less expensive and more widely available than monovalent sera, primarily due to the production process, which is simpler and can cover a broader array of antigens. In contrast, monovalent sera are more labor-intensive and specialized, thus have a higher cost.

In conclusion, the type of agglutinating serum used for specific applications depends on the purpose, sensitivity, and specificity of the test required. The decision between polyvalent and monovalent sera is primarily based on the clinical or research application, as well as the specificity and sensitivity of the assay.

Question 43

Why is the serum containing antibodies to several antigens obtained by immunizing the rabbit with microbes of a single species?

Answer 43

The serum containing antibodies to several antigens obtained by immunizing the rabbit with microbes of a single species is called polyvalent serum. The polyvalent serum is obtained by administering the same microbe to the rabbit several times, which stimulates the production of polyclonal antibodies against the microbe.

There are several reasons why immunizing rabbits with microbes of a single species can yield a polyvalent serum containing antibodies to several antigens:

1. Cross-reactivity: Some antigens of different strains or serotypes of the same species may share similar epitopes, which can result in cross-reactivity of the antibodies produced against one antigen to other antigens. This means that the antibodies produced against one strain or serotype may also recognize other strains or serotypes within the same species.
2. Polyclonal antibodies: The immunization of rabbits with microbes of a single species results in the production of polyclonal antibodies, which are a mixture of antibodies produced by different clones of B-cells. This can lead to the production of antibodies against multiple antigens of the same microbe.
3. Conserved antigens: Some antigens may be conserved across different strains or serotypes of the same species, which means that antibodies produced against one antigen may recognize other antigens within the species.

Polyvalent serum is useful for serological testing because it can detect antibodies against multiple antigens of the same species. This can be helpful in determining the serotype or strain of a microbe causing an infection or in estimating the prevalence of the pathogen in a population. However, polyvalent serum may not always provide the specificity required to differentiate between different strains or serotypes of the same species, which can limit its usefulness in certain diagnostic situations. Therefore, additional testing may be required to confirm the identity of the microbe causing an infection.

Question 44

What methods is the monoreceptor serum obtained with?

Answer 44

Monoreceptor serum, also known as monovalent serum, is obtained by immunizing animals, such as rabbits or mice, with a single antigen or epitope of a microbe. During the immunization process, the animal’s immune system produces a specific type of antibody called monoclonal antibody, which recognizes only one specific antigen.

There are different methods for producing monoreceptor serum, including:

1. Hybridoma technology: This method involves fusing a B-cell or plasma cell from an immunized animal with a transformed myeloma cell. The resulting hybrid cell or clone is immortal and produces a specific monoclonal antibody directed against a single epitope.
2. Phage display technology: This method involves creating a library of antibody fragments displayed on the surface of phage particles. The library is screened against the antigen of interest, and the phages that bind specifically to the antigen are selected. The antibody fragment is then produced and purified as a monovalent serum.
3. Recombinant DNA technology: This method involves cloning the gene encoding a specific antibody fragment and expressing it in a suitable host, such as bacteria or yeast. The recombinant monoclonal antibody fragment can then be purified and used as a monoreceptor serum.

The choice of method for producing monoreceptor serum depends on the antigen’s nature, availability, and the desired application. For example, hybridoma technology is widely used for producing monoclonal antibodies to most antigens, phage display technology is suitable for screening large numbers of potential antibodies, and recombinant DNA technology is useful for producing large quantities of monoclonal antibodies in a cost-effective and scalable way.

Monoreceptor serum has several applications, including serotyping of microorganisms, molecular antigenic characterization, and diagnostic assays for infectious diseases.

Question 45

What does the term “adsorbed agglutinating serum” mean?

Answer 45

Adsorbed agglutinating serum is a type of serum in which antibodies have been selectively removed or adsorbed against unwanted antigens, leaving only antibodies specific to the target antigen. This is achieved by exposing the serum to a mixture of cells or antigens that express the unwanted antigens, which absorb or remove the non-specific antibodies.

The term “agglutinating” refers to the ability of the serum to cause clumping or agglutination of cells or particles that express the target antigen. Agglutination is a visual test that allows the detection of antibodies in the serum that recognize the specific surface antigens on a microbe. When agglutinating serum is mixed with the target antigen, the antibodies in the serum bind to the antigens on the surface of the cells or particles, causing them to clump together.

Adsorbed agglutinating serum is useful in serological testing for infectious diseases because it provides a more specific and accurate identification of the microbe or its antigens. For example, in blood typing, an adsorbed agglutinating serum is used to selectively remove antibodies that react with unwanted blood group antigens, leaving only antibodies specific to the target blood group. This allows for a more accurate and specific determination of the blood type.

Adsorbed agglutinating serum is also used in serotyping of microbial pathogens, where it is essential to distinguish between closely related strains or serovars of a microbe. By selectively removing non-specific antibodies that cross-react with different strains or serovars, adsorbed agglutinating serum can provide a more accurate and specific serotyping result.