Immunology Flashcards
Where is the immune system located?
It’s scattered throughout the body
What is the role of the immune system? Describe two situations where it is necessary.
Its role is to protect the entire body at all times
1. From pathogens (bacteria, virus, parasite)
2. From altered body cells (cancer)
Describe two situations in which the immune system can “turn on us”.
The body will misrecognize cells as foreign in
1. autoimmune disorders
2. If tissues are tranplanted
What are the two components of the immune system?
- non-specific/ innate system
- Specific/ Adaptive
Of the two major components of the immune system, we are born with […]
both
Name two differences between innate immunity and adaptive immunity.
Non-specific:
Does not need to recognize a pathogen
Same response every time it sees the pathogen
Specific:
Requires to recognize the pathogen
Has a faster response the second time it sees the same pathogen
Explain the origin of vaccination
Smallpox disease led to lesions, which left behind scars called “pox”. Dr. Edward Jenner noticed that no milkmaids, who had gotten cowpox, had the marks of smallpox, leading him to assume that one protected the individual from the other. He took pus from a smallpox pustule and put it other the skin of another individual to inoculate them against smallpox and it worked.
What are the two categories of lymphoid organs? Explain the difference between them.
PRIMARY lymphoid organs
- Where the stem cells divide
- Where immune cells develop
SECONDARY lymphoid organs
- Sites where most immune responses occur
Immune cells are also known as..
leukocytes
Name the two primary lymphoid organs.
Bone marrow
Thymus
What is the immune function of the bone marrow?
It produces blood cells: B-cells and immature T-cells
It’s also where B-cells mature
What is the bursa and what is it homologous to in humans?
It’s homologue to the bone marrow since it also produces the B-cells
What is the immune function of the thymus?
It contains T-cells, dendritic cells, epithelial calls and macrophages
It’s also where T-cells mature
What happens to the thymus as we age?
it atrophies and can be almost gone with old age
Name the three secondary lymphoid organs.
Lymph nodes
Spleen
Lymphoid nodules
Where are lymph nodes found?
about 600 scattered throughout the body
What is the immune function of lymph nodes?
It filters the microbes before draining the lymphatic fluid into larger blood vessels
The macrophages inside the nodes phagocytize the microbes that enter the lymph
What is the immune function of the spleen?
Remove microbes and old erythrocytes
What is the immune function of lymphoid nodules?
Provide immunity in the mucosal-associated tissues
Give 3 examples of lymphoid nodules.
Tonsils
Appendix
Peyer’s patches
What are the two major categories of leukocytes?
Originating from the lymphoid or Myeloid committed cells
Name the 3 major types of lymphocytes.
T cells
B cells
NK cells
Where do each of the 3 lymphocyte types mature?
B cells in bone marrow
T cells in tymus
NK cells i’m not sure
Name the three types of T cells.
Cytotoxic
Helper
Regulatory
Myeloid leukocytes are divided into two major categories, […] and […]
granulocyte and agranulocyte
Name all the granulocytes and their function.
Eosinophils: destroy parasite
Basophils: release chemicals and histamine
Mast cells: release chemicals and histamine
Neutrophils: Phagocytes
Name all the monocytes and their function.
Macrophages and dendritic cells are there for phagocytosis
In innate immunity, what qualifies as the first and second line of defense?
FIRST: physical barriers
SECOND: cellular and humoral factors
Explain the first line of defense in innate immunity.
They are barriers to entry and can also creat an unpleasant environment for the microorganisms to live in
Name 5 physical barriers leading to innate immunity in the skin.
Tight junctions of the epithelia
Longitudinal flow of air or fluids
Fatty acids
Antibacterial peptides
Normal flora
Name 6 physical barriers leading to innate immunity in the gut.
Tight junctions of the epithelia
Longitudinal flow of air or fluids
Low pH
Enzymes
Antibacterial peptides
Normal flora
Name 3 physical barriers leading to innate immunity in the lungs.
Tight junctions of the epithelia
Movement of mucus by cilia
Antibacterial peptides
Name 2 physical barriers leading to innate immunity in the eyes and nose.
Tight junctions of the epithelia
Salivary enzymes –> lysozyme
When is the second line of defense in innate immunity needed?
When the foreign body goes through the physical barriers (first line), the second line of immunity is activated
Name 3 humoral factors in the second line of defence.
Inflammation and fever
Antimicrobial substances (complement)
Interferons
Name 3 cellular factors in the second line of defense.
Phagocytic cells
Cells with inflammatory mediators
NK cells
What are the 4 distinct signs and symptoms of inflammation and what are they caused by?
Redness: increased blood flow
Heat: increased blood flow
Pain: factors following injury
Swelling: humeral factors moving into the tissues
What are the first stage of inflammation?
There is vasodilatation to bring more blood resources (blood cells and plasma proteins) into the lesion. By doing that, the vessels are stretched and create more space between the cells of the vessels. That way, the vessels are more permeable and allow substances to go to the damaged site.
Give 3 examples of humoral antimicrobial substances.
Interferons
Complement
Iron binding proteins
Explain the function of interferons in the immune system.
a virus uses the infected cell to reproduce itself
Once a virus infects a cell, it will release interferons. Those are going to link to the interferon receptors on the uninfected cells. They will then be able to produce antiviral proteins before getting infected. When the cell IS INFECTED, it already had protein to prevent the replication of the virus.
What is a complement?
Plasma proteins with multiple functions to participate in fighting infections
Name the two main complement pathways and whether they belong to innate immunity or adaptive immunity.
The alternative pathway (innate)
The classical pathway (adaptive)
Explain how the alternative complement pathway works in innate immunity.
When there is an injury, the plasma protein moves into the tissue and attaches to the pathogen’s surface. The complement is then activated and opsonizes the pathogen (preparing it to be phagocyted)
Explain the function of complement C3b as an opsonin.
It sticks to the bacteria and makes the bacteria more recognizable to phagocytes since they have Cb3 receptors on their surface.
Given an example a humoral substance that is an iron-binding protein and explain its function.
Transferrin
When a bacteria is infecting an organism, it needs iron to replicate itself. However, once the body has identified a bacteria, it will produce more transferrin so it can pick up any additional iron. That way the bacteria can’t use it to replicate itself.
Give 2 examples of autoimmune diseases.
HIV AIDS and SCID
What are the two components of the second line of defense of the innate immune system?
The humoral and cellular factors
The major cellular factors in the second line of innate immune defense are […]
NK cells
Phagocytic cells
Cells with inflammatory mediators
What are NK cells? How do they act
They are cells that target virus-infected and cancer cells
Are NK cells antigen-specific?
No
NK cells kill infected cells by […]
They attack and kill the target cell by releasing a first molecule that punctures the infected cell and a second molecule that goes into the cell to kill it
Explain how the NK cell knows which cells to kill.
Normal body cells express a MHC 1 protein (cancels the other ligand). When the NK cells are not able to recognize that protein on a cell, it knows it’s foreign and knows to kill it
What is the function of phagocytes?
Non-specifically engulf microbial invaders
What are the two types of phagocytes? Explain the major difference between them.
Macrophages and dendritic cells are already in the tissue where there could be an injury
On the other hand, Neutrophils travel in the circulation and are going to be recruited at the site of injury.
Name the four steps of phagocytosis and intracellular destruction of a microbe.
Adherence (endocytosis)
Ingestion (phagosome)
Digestion (lysosome)
Killing (phagolysosome)
Explain the process of phagocytosis and intracellular destruction of a microbe.
The microbe in the ISF is brought in by endocytosis into the phagocyte. It’s kept in a phagosome so it doesn’t spread in the cytoplasm, and lysosomes are brought to from a phagolysosome. At that point. the bacteria is killed, and produces debris and/or a signal to send to other immune cells.
How do phagocytes recognize microbes?
They recognize structures that are not necessary from body cells and so are unique to microbial physiology. They are called Pathogen-Associated Molecular Patterns (PAMPs)
Macrophages recognize PAMPs using […]
Pattern Recognition Receptors (PRR) on their surface. They are Toll-Like Receptors (TLRs)
What are toll-like receptors?
They are transmembrane receptors with an extracellular domain that recognizes pathogens and an intracellular domain for signalling what was identified.
They are essential for microbial recognition via PAMPs by macrophages.
When toll-like receptors detect […], this starts the process of […]
PAMPs
Inflammation
Explain what happens when PAMPs get detected by toll-like receptors.
The macrophage is activated and signals are sent out to the body to active the inflammation process and recruit more immune cells to the site of injury, including neutrophils.
The first cell to be recruited once the process of inflammation has begun is […]
the neutrophil
The recruitment of neutrophils corresponds to the […] stage of inflammation
emigration of phagocytes [after vasodilatation]
Explain the first step in the emigration of phagocytes to the injured site.
The first step is chemotaxis. Once the toll-like receptors have detected PAMPs, they send out chemoattractants, which attract phagocytes (neutrophils) to the injured site.
Explain the second step in the emigration of phagocytes to the injured site.
Margination. The neutrophils stick to the surface of the blood vessels
Explain the third step in the emigration of phagocytes to the injured site.
Diapedesis. The neutrophils move across the capillary wall to act on the injury site.
Once the neutrophils have arrived at the injury site, explain what their function is.
They attack the bacteria and die in the process. By dying, they form NETs. Those slow down the bacteria and keep them stuck in some sort of glue-ish net.
NETs are made of […]
cytoplasmic proteins that come from the lysed neutrophil
Pus is comprised of […]
mixture of dead bacteria and neutrophils
What happens once the neutrophils have completed their role of creating the NET?
Thay die in the process
Explain how the specific branch of the immune system is activated.
The specific branch of the immune system is activated by the dendritic cells. When they clean up the dead bacteria/NETs, they bring back parts of the bacteria to its surface to present it in central nodules. That will activate other cells with the corresponding receptors and continue the immune response if necessary.
When phagocytes transport bacteria from the injury to the regional lymph node, they travel via the […], because […]
Lymph
otherwise bacteria would be carried trough the blood vessels
Name 3 other terms for antigen.
Immunogen
Allergen
Ligand
What is an antigen?
a material that that induces an immune response
The part of the antigen that is recognized by immune cells is the […]
the epitote
The transition from non-specific immunity to specific immunity occurs via […]the
dendritic cells
Explain what is meant by antigen presentation via phagocytes.
The phagocytes bring back a part of the bacteria to present it to the regional lymph nodules. This will activate the corresponding receptor and create an adaptive immunity
Specific/adaptive immunity is mediated by […]
Antibodies (humoral) and cells
What type of cell is involved in humoral specific/adaptive immunity? Explain how.
B lymphocytes
When they are activated, they transform into plasma cells. They then synthesize and secrete antibodies. They keep a memory of that for a better response next time.
What type of cell is involved in cell-mediated specific/adaptive immunity? Explain how.
Cytotoxic T-cells
They kill infected body cells, cancer cells and foreign cells
What are the two classes of MHCs? Explain the difference between them.
MHC 1: expressed on all nucleated cells to identify them as normal body cells
MHC 2: expressed on antigen-presenting cells in addition to MHC 1
Antigen-presenting cells include […]
Macrophages, Dendritic cells, B-cells
Do RBCs have MHCs on their surface? Explain.
No, they don’t have a nucleus. This is not a problem because they don’t have the other ligand that can activate NK cells.
Describe the purpose of MHC-II in the specific immune system.
In the adaptive immune system, T-cell receptors only recognize antigens that are presented on MHC 2 proteins. They are essential in the antigen-presenting process.
Explain the process through which MHC-II becomes associated with antigens.
the antigen-presenting cell first ingests the antigen
It is then digested into peptide fragments
Separately, the MHC 2 are synthesized
They are then fused
The MHC 2 is inserted into the membrane.
What are the three stages of a typical adaptive immune response to an antigen?
- Recognition of an antigen by a lymphocyte
- Lymphocyte activation
Attack launched by the activated lymphocyte and its secretions
The adaptive immune system involves which cells?
B ant T cells
What is the role of T cells in the adaptive immune system?
They are the cell-mediated response
Cytotoxic T-cells attack specific cells by rocognition
Explain what happens to B and T cells once they enter the secondary lymphoid organs.
IF they’re activated by the right antigen, they are going to start the adaptive immune response
Explain how helper T cells, B cells, and cytotoxic T cells interact after encountering an antigen.
The Helper T-cell will be necessary to fully activate the B-cells and the cytotoxic T-cells even when both have encountered the same same bacteria
How do T-cells and B-cells recognize specific microbes in order to develop the correct immune response?
They have surface receptors corresponding to a specific antigen that will then activate the B or T-cell
Describe the match between a T helper cell and an antigen presenting cell.
You first have a specific recognition of the new MHC-II and peptide complex (on the APC) from the T cell receptor. There is also a co-reception done by the CD28 (t-cell) to the C7 (APC).
What is the role of B cells in the adaptive immune system?
They are the humeral mediated response
They produce antibodies
What is checkpoint inhibition?
Name the cells and membrane proteins
It is a process that serves as a “shut-off” control between the APC and the T-cell. On the T cell, the CD28 will be displaced and replaced with another receptor. This will stop the release of cytokines and slow down the immune response
After the helper T cell is activated, the next cell to be activated is the […]
B-cell
Explain how the B cell gets activated after the helper T cell has been activated.
The B-cell must also have a recognition event with the pathogen presented on the dendritic cell. The helper T-cell then interacts with the B cell directly by linking the T-cell CD40L proteins with the B cell CD40 protein. The T-cell then releases cytokines, which leads to the activation of the B cell and its production of antibodies.
The activation of the T-cells and B-cells takes place in […]
in the lymph nodes and the spleen
Why does the B-cell also have to have its own recognition event with the antigen?
It is another checkpoint in addition to the T helper to avoid a wrong response
Explain what happens once the B-cell has been activated.
In the lymph node or spleen, the B cell will divide. One will turn into a memory cell to increase the response speed during the next infection. They stay in the organ. The other will divide into two plasma cells, which will produce specific antibodies, which will be secreted into the circulation to fight the pathogen.
Which types of cells produce memory cells?
ALl of them: B and both T-cells
What are the three events required for the activation of the T helper cell?
Macrophage (ACP) + Th cell
MHC-II + peptide - TCR
B7 + Co-receptor CD28
Cytokines from APC stimulate the T-cell
Recall: when the body is in the process of fighting infection, how will serum protein electrophoresis results differ from normal?
The gamma globins are going to be produced in larger quantities to fight the infection, and so on the electrophoresis, the gamma peak will be higher.
Describe the structure of plasma cells and how that corresponds to their purpose.
Plasma cells have a membrane filled with endoplasmic reticulum dedicated to producing thousands of antibodies per minute.
How long do plasma cells live for?
about a week
Antibodies, also called […], belong to the group of proteins called […].
immunoglobins
globins
Describe the structure of antibodies.
They have a general Y shape with two identical heavy chains and two identical light chains. There are two important regions, the variable region [FAB] and the Constant region [Fc]
Explain what the FAB region is on the antibody.
It’s a region variable. It’s where the antigen will bind and where the specific recognition will take place. Depending on the pathogen they are recognizing, the sequence will be different.
Explain what the Fc region is on the antibody.
This sequence is the same for all antibodies of a given class
Antibody class is determined by […]
The sequence of the constant region Fc of the antibody
What are the 5 antibody classes?
IgG
IgA
IgM
IgD
IgE
Describe the structure of the major antibody classes.
IgG : Y shape
IgA : Bi-Y shape
IgM: 5 Y shapes on one center
IgD: Y shape specific to prenatal
IgE: Y shape to specific allergies
What is the most abundant antibody class?
IgG
What is distinctive about IgA antibodies?
They are found in Mucosal-Associate tissues and breast milk
What is distinctive about IgM antibodies?
They are important in the activation of complements
Summarize how antibody-mediated immunity works.
First, the B-cells are activated in the spleen, lymphoid nodule or lymph nodes. They will produce clones that undergo a clonal selection between plasma cells to secret specific antibodies or Memory cells for a faster response if the antigen is seen again.
What is the purpose of memory cells?
Fight the infection faster when the antigen is seen the next time
What are the two ways in which antibody immunity can be acquired?
Actively or passively
Explain what active antibody immunity is.
It’s when the person’s own immune system responds to the pathogen and forms long-lasting protection
What are the two types of active antibody immunity? Explain the difference between them.
Natural: immunity developed with a natural exposure to the antigen
Artificial: immunity developed with a purposeful exposure to the antigen
What type of antibody immunity is conferred when someone gets a vaccine?
Active artificial immunity
What type of antibody immunity is conferred when someone is exposed to the flu virus?
Active natural immunity
Explain what passive antibody immunity is.
When a person receives antibodies from another person, it creates temporary protection. That is because their body did not go through the physiological process of secreting antibodies and did not make memory cells either.
What are the two types of passive antibody immunity? Explain the difference between them.
Natural: IgG from the mother through the placenta or IgA through the breast milk
Artificial: A serum with another persons antibodies
What is a vaccine?
It is a small quantity of living or dead bacteria, toxins or harmless antigenic molecules derived from the pathogen.
Explain the general principle behind vaccination.
The principle is for the body to be exposed to the pathogen in a harmless way to have an active immune response that includes the formation of memory cells. So if the pathogen is seen again, the reaction will be more effective and faster.
Explain the importance of passive immunity for infants.
For the first months of life, the infant’s antibody-synthesizing capacity is poor. For protection, they get their antibodies from the mother through breast milk
What are the 6 major roles of antibodies in fighting infection?
Neutralizing the antigen
Agglutination of antigens
Precipitation of antigens
Activating a complement
Opsonization
Antibody-Dependant Cellular cytotoxicity
Explain how antibodies neutralize antigens.
When the bacteria comes in contact with the antigen, it is neutralized. This process is specific to an antigen and stops them from acting and multiplying
Explain how antibodies agglutinate antigens.
They are multiple antibodies grabbing multiple antigens so they are all held together to slow them down, pr5event their division and localize them for the pgagocytes
Explain how antibodies precipitate antigens.
When an antigen is soluble, contact with the antibody will precipitate it and the antigen can no longer act
Explain how antibodies activate complement.
The interaction of the antigen, antibody and the binding of C1 leads to the classical complement pathway. This results in a membrane attack complex that makes a whole in the surface of the antigen and killing it.
Explain how antibodies aid in opsonization.
Phagocytes also have receptors for the Fc portion of the antibody. So when the antibody interacts with the antigen, the phagocyte can recognize it faster.
Explain how antibodies contribute to antibody-dependent cellular cytotoxicity.
NK cells have Fc receptors on their surface and a specific antibody binds to the target cell (Fc on the NK and FAB on the target). This interaction activates the release of the two molecules from the NK cell to kill the target cell.
Describe the progression of antibody production after initial exposure to the antigen.
The production is slow and the final response is relatively low
Describe the progression of antibody production upon subsequent exposure to an antigen.
When the body in exposed to the pathogen again, the response is a lot faster and has a lot more antibodies involved making it a lot more efficient.
What does it mean for a lymphocyte to gain immunocompetence?
It’s when a lymphocytes develops a antigen receptor.
What is the cellular component of the adaptive immune system?
Cytotoxic T cells directly attack antigen-bearing cells.
and B cells that release antibodies
Lymphocytes develop receptors for every pathogen that we might experience by the process of […]
immunocompetence
What are the two enzymes involved in somatic hypermutation?
RAGs: Recombination Activating Genes
TdT: terminal Deoxynucleotidyl Transferase
Describe the function of RAGs in immunocompetence.
splice out the gene segments of the V, D and J chains to create a more specific DNA eventually leading to speciation
Describe the function of TdT in somatic hypermutation.
TdT inserts additional nucleotides at the junctions between gene segments. This will ultimately make more combinations possible for antigen receptors
What is the end product of somatic hypermutation?
The end result will be mRNA with one variable region made up of a V, D, and J gene, and one constant region, made up of a C gene.
The category of antibody (IgE, IgG, etc.) is determined by its […] region.
FC
When you get an infection for the first time, the first antibodies to be produced in the primary response are […]. because […]. They are followed by […] in [smaller/equal/greater] quantities.
IgM because they activate complements, which aid with the immune response
IgG, equal
The secondary response to an infection involves the production of which antibody type(s) and in what quantities?
The IgM in the same quantity as the primary response and IgG in a larger quantity than the primary response
When you get an infection in mucosal tissue, the major antibody to be produced will be […]
IgA
How does the body know not to attack its own cells?
It recognizes the major histocompatibility complex (MHC) of the body, which is unique (except in identical twins). During development, any lymphocytes that might target our own body are removed.
The process of getting rid of lymphocytes that might attack our own body cells is called […], which has the end goal of […]. When does it occur?
Clonal deletion/clonal inactivation, immune tolerance. It occurs during fetal and early postnatal life.
Describe the steps by which the development of T cell tolerance occurs
- any T cell that cannot recognize MHC II molecules will be destroyed
- T cells that recognize MHC Class I-self peptide complexes are negatively selected to prevent self-attack.
[…]% of T cells never leave the thymus. Why?
95, because they get destroyed to provide immune tolerance
Why do we get an amplified immune response upon second exposure to disease?
When creating memory cells, the concentration of B and T cells that have receptors for specific antigens increases. On the second response, the chances of a antigen activating a lymphocyte is greater and will happen quicker.
What is the difference between an exogenous antigen and an endogenous antigen?
exogenous antigen is a foreign body and is free in the tissue when attacking whereas endogenous antigen goes inside the body cells to multiply and attack.
How does the response of the immune system differ for endogenous antigens as opposed to exogenous antigens?
With endogenous antigens, Cytotoxic T cells will be activated
Explain the process by a endogenous antigen infects a body cell .
The infected body cell is always producing MHC I molecules for itself. When the virus has infected it, the MHC I binds with a peptide fragment of the antigen. The molecule is then inserted into the plasma membrane and could be detected may a Tc cell.
Explain how cytotoxic T cells deal with infected body cells once they’ve been activated.
- The Tc cell will detect the antigen on the MHC I molecule
- the Th cell will fully activate the Tc cell
- The Tc cell is activated and creates memory cells
- the activated cell release perforin and granzymes to kill the infected cell
When does the proliferation of cytotoxic T cells take place relative to the recognition event with an infected cell?
Only when the Tc cell had a recognition event and when it was stimulated by the release of cytokines from the Th cell.
What is the fate of cytotoxic T cells after they’ve interacted with and killed a body cell?
They will travel to the next infected cell until there are no more left
Name 5 factors that might alter resistance to infection.
- Protein-calorie malnutrition
- Preexisting disease
- Stress and state of mind
- Sleep deprivation
- Modest PA (decreases resistance)
Explain how protein-calorie malnutrition affects resistance to infection.
Even if the lymphocytes are synthesized, they need other materials to be activated and so a malnutrition results in a decreased immune response.
How does having AIDS affect the immune system?
Infect and kill Th cells resulting in impaired immune responses.
How does having SCID affect the immune system?
absence of B, T and some times NK cells
Give 5 examples of situations of harmful immune responses.
- Tissue graft rejection
- transfusion reaction
- Allergy
- Autoimmune disease
- Excessive inflammatory responses
Explain why graft rejection/the rejection of organ transplants might occur.
The MHC I proteins in cells and MHC II proteins in macrophages are different for each person, so the recipient will recognize the new MHC proteins as foreign. The recipient’s Tc and Th cells will kill them.
Give an example of a drug that can prevent graft rejection and explain how it works.
Cyclosporine blocks the production of Th cells, meaning Tc cells can’t be activated
What is a potential side effect of cyclosporine? Explain why.
It does not only block T cells from attacking the graft cells, it will also have a lowered immune response to all antigens.
Explain why transfusion reactions might occur. Give an example.
Even tho RBCs don’t have MHC proteins, their ABO system of carbohydrates can be recognized as foreign in the blood. A blood type A receiving from a B will have a reaction since they already have B antibodies in their blood.
For blood groups A, B, AB, and O, what are the antigens on the individual’s RBCs and the antibodies present in their blood?
A: B antigens
B: A antigens
AB: no antigens
O: both antigens
What is an allergic reaction?
A reaction to a substance that is tolerated well by most. the reaction is restricted to the site of injury
What are the two types of allergic reactions?
Immediate hypersensitivity
or delayed hypersensitivity
The major leukocyte type involved in allergic reactions is […], which secrete […]
Mast cells, Histamine (inflammatory reaction, vasodilator)
What is anaphylaxis? How does it occur?
Severe hypotension and bronchiolar constriction are caused by a large amount of mast cells or basophil histamine entering the circulation.
Exaggerated inflammatory reactions.
What is autoimmune disease?
an inappropriate immune attack triggered by body proteins acting as antigens
