Immunity

Question 1

Innate Immunity- define, characteristics, and its role

Answer 1

Define:
First line of defense against pathogens present from birth.

Characteristics:
-Physical barriers are skin, mucous membranes, and acidic stomach secretions. First line of defense always at work.

-Second line of defense inflammatory response- innate triggers inflammation to combat infections and initiate immune response.

Role: immediate protection against pathogens, recognizes patterns on pathogens and triggers an immune response.

Question 2

Acquired Immunity (aka Adaptive Immunity)- define, characteristics, and its role

Answer 2

Define:
specific, long-lasting and acquired immune response that develops throughout life following exposure to pathogens, vaccines, or other antigens. It provides targets and long-lasting protection against specific pathogens.

Characteristics:
-Specific Response: Adaptive immunity is highly specific, targeting specific antigens on pathogens. It is characterized by immunological memory, allowing a faster and stronger response upon reinfection.

• Cellular and Humoral Immunity: Adaptive immunity involves two main branches - cellular immunity mediated by T lymphocytes and humoral immunity involving B lymphocytes and antibodies.
• Antigen Recognition: Adaptive immune cells have receptors that can specifically recognize and respond to antigens

Role:
-Memory Response: Adaptive immunity forms immunological memory, enabling a quicker and more robust response upon subsequent exposure to the same pathogen. Acquired immunity involves the development of immunological memory. After an initial exposure to an antigen, the immune system “remembers” the specific pathogen and mounts a rapid, robust response upon subsequent encounters

-Tailored Response: Adaptive immunity can adapt and mount a specific response to a wide range of pathogens, providing personalized protection against diverse threats.

Two arms of adaptive immunity:
-Cellular Immunity: Involves T lymphocytes (T cells) that directly attack infected or abnormal cells and coordinate immune responses.

-Humoral Immunity: Involves B lymphocytes (B cells) that produce antibodies (immunoglobulins) to target pathogens, neutralize toxins, and tag particles for
destruction.

Question 3

Innate Vs Adaptive Immunity- level of specificity and response

Answer 3

-Innate Immunity: The responses of innate immune cells are generalized and do not change upon repeated exposure to the same pathogen. They recognize and respond to common features shared by various pathogens. Does not involve specific antibodies. Instead, it relies on protein mediators, such as complement proteins and cytokines, to carry out responses against pathogens.

-Adaptive Immunity: Adaptive immune responses are highly specific to the invading organism. Following exposure to a pathogen, adaptive immune cells develop memory cells that remember the antigen. Upon reinfection, the immune response is faster and
more effective due to this memory. Adaptive immunity involves the production of specific antibodies (immunoglobulins, Ig) by B cells. These antibodies are highly specific to the antigens of the invading pathogen. They provide long-term protection and memory, allowing for a quicker and more effective response upon re-exposure to the same pathogen.

Question 4

Antigen- define and function with adaptive immunity

Answer 4

Definition:
An antigen is a molecule that can trigger an immune response in the body. Antigens can be foreign substances like bacteria, viruses, allergens, or fungi, as well as self-antigens in certain autoimmune conditions.

Function in Adaptive Immunity:
Antigens are essential for initiating the adaptive immune response. The immune system recognizes antigens as foreign invaders and mounts specific responses to combat and eliminate them. Haptens are small molecules that can elicit an immune response only when attached to a larger carrier molecule

Question 5

Antibody- define and function with adaptive immunity

Answer 5

Definition:
Antibodies, also known as immunoglobulins, are proteins produced by B lymphocytes in response to the presence of antigens. They are highly specific to the antigens they recognize.

Function in Adaptive Immunity:
-Short-Term Immunoglobulins:
▪ IgM: IgM is the first immunoglobulin produced in response to an
infection. It is efficient at neutralizing pathogens and activating the
complement system. IgA and IgE are also considered short-term
antibodies involved in mucosal immunity and allergic responses,
respectively.

-Long-Term Immunoglobulin:
▪ IgG: IgG is the main antibody class responsible for long-term immunity. It provides lasting protection against pathogens and enhances immune memory.

Question 6

Antigen Presenting Cells- define and function with adaptive immunity

Answer 6

Definition:
Antigen Presenting Cells are specialized immune cells that detect, engulf (phagocytosis), process, and present antigenic peptides to T lymphocytes to initiate adaptive immune responses.

Function in Adaptive Immunity:
APCs play a crucial role in activating T cells, which are key players in the adaptive immune response. By presenting antigens to T cells, APCs ensure that the adaptive immune system can specifically target and eliminate pathogens. Examples of APCs include dendritic cells, macrophages, and B cells.

In brief, in adaptive immunity, antigens are recognized as foreign invaders, antibodies (immunoglobulins) are produced to specifically target these antigens, and antigen-presenting cells play a vital role in initiating the adaptive immune response by presenting antigens to T cells for activation.

Question 7

Immunoglobulins- define

Answer 7

AKA antibodies, are glycoproteins produced by plasma cells, a type
of white blood cell derived from B cells, in response to the presence of antigens (foreign substances or pathogens) in the body. These antigen-specific proteins are an essential part of the immune system’s response to infections and other threats.

Question 8

Immunoglobulin A (IgA)- define

Answer 8

Found predominantly in mucosal areas such as the respiratory and gastrointestinal tracts, where it plays a crucial role in mucosal immunity and defense against pathogens.

IgA Opsonization: IgA antibodies can enhance phagocytosis by opsonizing pathogens, making them more recognizable to phagocytic cells for engulfment and destruction.

Question 9

Immunoglobulin M (IgM)- define

Answer 9

The first antibody produced in response to an infection, typically forming pentamers. IgM is involved in the primary immune response and acts as a potent activator of the complement system.

IgM Complement Activation: IgM antibodies can activate the complement system, a group of proteins that enhance the immune response by promoting inflammation, opsonization (marking pathogens for phagocytosis), and cell lysis.

Question 10

Immunoglobulin G (IgG)- define

Answer 10

The most abundant antibody in the bloodstream, providing long-term immunity. IgG can cross the placenta to confer passive immunity to a developing fetus and plays a key role in immune memory.

Immune Memory: IgG antibodies provide long-lasting immunity due to their ability to “remember” previous infections. Upon re-exposure to the same pathogen, an immune memory response is mounted more quickly and effective

Question 11

Immunoglobulin E (IgE)- define

Answer 11

Primarily involved in allergic responses and defense against parasitic infections. IgE binds to mast cells and basophils, triggering the release of histamine in response to allergens

Question 12

Immunoglobulin D (IgD)- define

Answer 12

Found mainly on the surface of B cells, where it functions as a receptor for antigen recognition. IgD is involved in B cell activation and maturation.

Question 13

Function of immunoglobulin, Opsonization- define

Answer 13

Immunoglobulins mark pathogens for phagocytosis by immune
cells, enhancing the clearance of microbes. Antibodies can opsonize antigens by binding to their surfaces, making them more recognizable to phagocytic cells like macrophages and neutrophils.

Role in Protection: Opsonization enhances the process of phagocytosis, as the antibodies coating the antigen mark it for engulfment and destruction by immune cells, thereby aiding in the clearance of pathogens from the body.

Question 14

Function of immunoglobulin, Neutralization- define

Answer 14

Antibodies can neutralize pathogens by preventing them from
binding to host cells or by blocking their activity. They bind to and inactivate harmful components, such as toxins or viral particles, preventing them from interacting with host cells.

Role in Protection:
By neutralizing antigens, antibodies block the antigen’s ability to
cause harm, thereby reducing the threat posed by the antigen to the host.

Question 15

Function of immunoglobulin, Complement Activation- define

Answer 15

Antibodies can trigger the complement system, a cascade of proteins that amplify the immune response, leading to inflammation and pathogen elimination

Question 16

T cells- maturation, immunity, antigen response, mature cell result, and impairment consequences.

Answer 16

Maturation: T cells mature in the thymus gland

Immunity: T cells are key players in cell-mediated immunity, responding to intracellular pathogens and abnormal cells (e.g., virus-infected cells, cancer cells).

Antigen Response: T cells recognize antigens presented by antigen-presenting cells and respond by directly killing infected cells (cytotoxic T cells) or coordinating immune responses (helper T cells).

Mature Cell Result: Mature T cells give rise to various subtypes, including cytotoxic T cells, helper T cells, and regulatory T cells, each with specific roles in immunity.

Impairment: Impaired T cell function can lead to compromised cell-mediated immunity, making individuals more susceptible to intracellular pathogens (opportunistic infections) and cancer.

Both T cells and B cells play critical roles in the adaptive immune response. T cells primarily target intracellular pathogens and abnormal cells. Compromised T cell function can hinder cell-mediated immunity, allowing intracellular pathogens to thrive.

Question 17

B cells- maturation, immunity, antigen response, mature cell result, and impairment consequences.

Answer 17

Maturation: B cells mature in the bone marrow

Immunity: B cells are involved in humoral immunity, producing antibodies that target extracellular pathogens (e.g., bacteria, toxins)

Antigen Response: B cells recognize antigens directly and differentiate into plasma cells that produce antibodies targeting the specific antigen

Mature Cell Result: Mature B cells differentiate into plasma cells that produce antibodies to neutralize pathogens and memory B cells for future immune responses

Impairment: Impaired B cell function can result in decreased antibody production, reduced ability to fight off extracellular pathogens, and increased susceptibility to infections.

Both T cells and B cells play critical roles in the adaptive immune response. B cells combat extracellular pathogens by producing antibodies. B cell function can impair humoral immunity, leading to increased vulnerability to extracellular pathogens.

Question 18

Agglutination- explain how it works and its role (how antibodies provide protection from antigens)

Answer 18

Explanation: Antibodies can cause agglutination by cross-linking multiple antigens together, leading to the formation of antigen-antibody complexes or clumps.

Role in Protection: Agglutination helps aggregate antigens, making them easier for phagocytic cells to engulf and clear in larger, more manageable clusters, enhancing the immune response’s efficiency.

Question 19

Precipitation- explain how it works (how antibodies provide protection from antigens)

Answer 19

Explanation: Antibodies can promote precipitation by making soluble antigens insoluble, causing them to form complexes that precipitate out of solution.

Role in Protection: Precipitation of antigens leads to their aggregation and deposition, facilitating their removal from circulation and clearance by phagocytic cells, contributing to the host’s defense against the antigens.

Question 20

Acquired (active) Immunity- define

Answer 20

Develops when the immune system is exposed to antigens through infection or vaccination, leading to the production of antibodies and memory cells post exposure. Provides long-term protection and immunological memory to specific pathogens, offering protection upon re-exposure.

The immune response originates from the
individual’s immune system activation and requires exposure to antigens to stimulate the immune response.

Examples:
Immunity developed after vaccination or recovery from infection, where the immune system generates a specific response against the pathogen

Involves the body’s immune response to antigens, providing long-term protection. Playing an essential role in protecting individuals from infectious diseases and contributes to overall immune defense strategies.

Question 21

Passive Acquired (active) Immunity- define

Answer 21

Occurs when pre-formed antibodies are transferred from another individual or animal, providing immediate but temporary protection. Examples include maternal antibodies passed through breastfeeding or injection of immunoglobulins for immediate protection. Immediate but short-lived protection, as the acquired antibodies eventually degrade and are no longer present in the recipient’s system.

Response is derived from pre-formed antibodies
introduced from an external source. Does not involve the individual’s immune system activation but
offers immediate protection without the need for antigen exposure.

Refers to the transfer of antibodies from one individual to another, providing immediate protection against a specific pathogen. This can occur naturally, such as when a baby receives antibodies from the mother through the placenta or breast milk, or artificially through medical interventions like receiving antibodies through injections. Passive immunity is
temporary, as the recipient’s body does not produce its own antibodies.

Examples:
Transfer of maternal antibodies to a newborn through breastfeeding or placental transfer, as well as the administration of pre-formed antibodies (e.g., in cases of rabies exposure).

The immediate but temporary transfer of
antibodies, offering immediate protection without immune memory. Playing an essential role in protecting individuals from infectious diseases and contributes to overall immune defense strategies.

Question 22

Natural passive immunity- define

Answer 22

This occurs when antibodies are passed from mother to fetus through the placenta during pregnancy or through breast milk after birth. This type of immunity provides immediate protection to the newborn against certain diseases until their immune system matures

Question 23

Artificial passive immunity- define

Answer 23

This involves the introduction of antibodies into an
individual’s body that are produced by another organism. This can be done therapeutically with injections of antibody-containing blood plasma or serum from humans or animals that have been previously exposed to a particular pathogen. Artificial
passive immunity is used in situations where immediate protection is needed or when the
individual’s immune system is compromised

Question 24

During fetal and newborn development, there are key time periods that are important for
immunity- maternal antibodies, T/B cell production, weak leukocytes at birth, breast milk and immunoglobulins.

Answer 24

Maternal Antibodies: Maternal antibodies are passed from the mother to the fetus during pregnancy, providing passive immunity. These antibodies protect the infant until about 37-40 weeks of gestation, and their levels decrease after birth. The maternal antibodies received can last for about 6 months in the newborn’s system, offering protection during the initial months of life.

2. T and B Cell Production: Production of T and B cells, key components of the immune system, begins around 6-8 months after birth. These cells play a crucial role in recognizing and fighting off pathogens. The immune system of newborns is not fully developed at birth, so the production of these cells is a significant milestone in building immunity.
3. Weak Leukocytes at Birth: Leukocytes, which are white blood cells involved in immune responses, are relatively weak and less lethal in newborns. The immune system is generally immature at birth, making newborns more susceptible to infections until their immune system strengthens over time.
4. Breast Milk and Immunoglobulins: Breast milk contains various immunoglobulins, such as IgA, IgG, and IgM, which are types of antibodies that confer passive immunity to the infant. These antibodies help protect the newborn against infections, providing an
   additional layer of defense while the infant’s immune system continues to develop.

Overall, understanding these key time periods and immune components in fetal and newborn
immunity highlights the importance of passive immunity from maternal antibodies and breast
milk in providing initial protection until the infant’s own immune system matures.

Question 25

Immunity system change with age- T/B cells, chronic inflammation, effect on chronic illness.

Answer 25

-T Cells: The thymus, where T cells mature, gradually shrinks with age, leading to a decline in the production of new T cells. This can weaken the adaptive immune response and reduce the ability to combat new pathogens.

-B Cells: While the number of B cells remains relatively stable, the diversity and effectiveness of their antibody production can decline. This may result in a reduced ability to mount robust immune responses to infections and vaccinations.

-Chronic inflammation: With age, there is a tendency for the immune system to become more chronically
activated, leading to a state of low-grade inflammation known as “inflammaging.” This sustained inflammatory response can contribute to the development of various age-related diseases, including cardiovascular disease, diabetes, and
neurodegenerative disorders.

-Chronic illness: The changes in T and B cell function, coupled with chronic inflammation, can have a detrimental impact on the development and progression of chronic illnesses. For example, a weakened immune response may make older adults
more susceptible to infections, while chronic inflammation can exacerbate conditions such as arthritis, Alzheimer’s disease, and cardiovascular issues.

-Additionally, the decline in immune surveillance with age can lead to an increased risk of cancer development, as the immune system may be less effective at recognizing and eliminating cancerous cells.

In summary, aging is associated with alterations in both the innate and adaptive immune responses, including changes in T and B cell function, increased chronic inflammation, and a higher susceptibility to chronic illnesses

Question 26

Immune hypersensitivity reactions

Answer 26

Exaggerated or inappropriate responses of the immune system to antigens, leading to tissue damage. There are four types of hypersensitivity reactions (Type I, II, III, and IV), each characterized by distinct immune mechanisms and responses. Here,
we will focus on distinguishing Type I, Type III, and Type IV hypersensitivities:

1. Type I Hypersensitivity (Immediate Hypersensitivity):

-Mechanism: Type I hypersensitivity reactions are mediated by IgE antibodies bound to mast cells or basophils. Upon re-exposure to an allergen, cross-linking of IgE antibodies triggers the release of inflammatory mediators like histamine, leading to rapid onset of symptoms.

-Example: Allergic reactions such as hay fever, asthma, hives, and anaphylaxis are
classic examples of Type I hypersensitivity

-Timing: Symptoms typically develop within minutes to a few hours after exposure to the allergen.

-Treatment: Antihistamines, corticosteroids, and in severe cases, epinephrine (EpiPen) are commonly used for treatment.

2. Type III Hypersensitivity (Immune Complex-Mediated Hypersensitivity):

-Mechanism: Type III reactions occur when immune complexes (formed by antigen-antibody binding) deposit in tissues and activate complement, leading to inflammation and tissue damage.

-Example: Diseases like systemic lupus erythematosus (SLE), rheumatoid arthritis, and glomerulonephritis are associated with Type III hypersensitivity.

-Timing: Symptoms typically manifest a few hours to days after exposure to the
antigen.

-Treatment: Treatment may involve immunosuppressants, anti-inflammatory
medications, and management of underlying conditions.

3. Type IV Hypersensitivity (Delayed-Type Hypersensitivity):

-Mechanism: Type IV reactions involve sensitized T cells (mainly CD4+ and CD8+ T cells) recognizing antigens and releasing cytokines that recruit and activate immune cells, leading to tissue damage.

-Example: Contact dermatitis (e.g., poison ivy reaction), graft rejection, and some autoimmune diseases like multiple sclerosis are examples of Type IV hypersensitivity.

-Timing: Symptoms typically develop over 24-72 hours after exposure to the
antigen.

-Treatment: Topical steroids, immunosuppressants, and avoidance of triggering
antigens are common strategies for managing Type IV hypersensitivity reactions.

In brief, Type I hypersensitivity involves IgE-mediated mast cell activation, Type III hypersensitivity is characterized by immune complex deposition, and Type IV hypersensitivity is T cell-mediated. Understanding the differences in mechanisms and clinical manifestations of these hypersensitivity reactions is crucial for accurate diagnosis and appropriate management of immune-mediated disorders.

Question 27

Effect of stress on the immune system

Answer 27

Stress can lead to a decrease in the number of circulating lymphocytes, including T cells and B cells. Chronic stress can dysregulate the immune response, making individuals more susceptible to infections and inflammatory conditions.

Question 28

Effect of nutrition on the immune system

Answer 28

Poor nutrition can result in decreased T and B cell function, impairing the body’s ability to mount effective immune responses. Deficiencies in essential nutrients like vitamins and minerals can also affect complement activation, an important component of the innate immune system

Question 29

Effect of specific immune deficiencies on the immune system

Answer 29

Zinc Deficiency: Zinc is crucial for the development and function of immune cells. Zinc deficiency has been associated with impaired immune response,
increased susceptibility to infections, and delayed wound healing.

Vitamin Deficiencies (B12, A, C, E):
▪ Vitamin B12: Deficiency can lead to decreased production of white blood cells and impair the function of T and B cells, impacting immune
responses.

▪ Vitamins A, C, E: These vitamins are antioxidants that play essential roles in immune function. Deficiencies can compromise immune surveillance and response to pathogens

Question 30

Effect of cancer on the immune system

Answer 30

Cancer can dysregulate the immune system by producing cytokines that damage surrounding cells, impair immune function, and create a pro-inflammatory environment. Additionally, the presence of cancer can lead to nutritional deficiencies that further weaken the immune response.

Question 31

Effect of immunosuppression on the immune system

Answer 31

Immunosuppression targets immune cells, particularly T cells, leading to a weakened immune response. This can increase susceptibility to infections, autoimmune disorders, and certain cancers as the body’s ability to mount an effective immune defense is compromised.