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58 Cards in this Set
- Front
- Back
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What are the phases in a humoral immune reaction?
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1. Recognition
2. Activation 3. Effector 4. Decline/homeostasis 5. Memory |
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What types of microbes stimulate antibody production?
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ONLY extracellular
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What are the responding lymphocytes to an extracellular microbe stimulation of humoral immunity?
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Bcells
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What are the effector mechanisms of Bcells?
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Antibody production
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What are the functions of the Antibodies?
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-Blocking infections
-Elimination of extracellular microbes |
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How does recognition occur in an initial, primary immune response? Where does it occur?
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Microbe binds to a naive, IgM+ IgD+ Bcell, crosslinking at least two antibodies. Occurs in follicles in lymph nodes.
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What happens when microbe binds a naive Bcell?
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It activates the Bcell
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Is Microbial binding the only thing that activates Bcells?
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No, Thelper cells and other stimuli also activate naieve Bcells.
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What does an activated Bcell do?
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-Clonally expands
-Differentiates |
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What are 4 types of cells that Bcell clones can differentiate into?
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1. Ab-secreting effector cells that secrete IgM
2. Ab-secreting cells that secrete IgG or other classes 3. High-affinity Ig-expressing Bcells via affinity maturation 4. Memory Bcells |
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When Thelper cells help stimulate Bcells, where does the interaction occur?
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Near the paracortex at the marginal zone around a primary follicle.
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What important function is mediated by humoral immunity and antibody production that is not conferred by other mechanisms?
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PREVENTION of infection by viruses, bacteria and parasites.
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In what forms are each of the antibody isotypes found?
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Monomers: IgG, IgD, IgE
Dimer: IgA Pentamer: IgM |
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When antigens initially stimulate Ab secretion in the peripheral lymphoid organs, where does the Ab go?
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Into the bloodstream to be
1. delivered to the infection site 2. to mucosal secretions to prevent microbe entrance |
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When Ab's use the Fc region to activate effector mechanisms to eliminate microbes/toxins, what are 3 things they depend on?
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1. Fab region recognition of the particular pathogen/toxin
2. Phagocyte and Complement participation 3. At LEAST 2 Ig molecules crosslinking the antigen |
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When is protection against a specific antigen conferred during a humoral response?
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-During the first week of the primary infection
-Immediately upon 2ndary infection |
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What are the 4 categories of antibody effector functions?
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1. Microbe/toxin neutralization
2. Opsonization/phagocytosis 3. ADCC 4. Complement activation |
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How do you remember the effector functions?
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Christine Noac
-Neutralize -Opsonize -ADCC -Complement |
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When Bcells differentiate into plasma + memory cells, which secrete Antibody?
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-Plasma cells
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How do memory cells function?
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By retaining their capacity to secrete Ab and doing so upon 2ndary exposure to the antigen.
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What does vaccination achieve?
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The differentiation of memory cells, which will confer immediate antibody secretion and protection upon a real exposure.
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What is the general goal of Isotype switching and Affinity maturation?
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To enhance the protective functions of antibodies.
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How is affinity maturation triggered?
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By prolonged/repeated antigen stimulation
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How is affinity maturation achieved for a vaccination?
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By giving booster shots
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Which antibody isotype has the most effector functions?
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IgG
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What are the 6 effector functions of IgG?
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1. Neutralization
2. Opsonization 3. ADCC via NK cells 4. Complement activation (classical pathway) 5. Neonate immunity 6. Feedback Bcell inhibition |
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What is the main function of IgM?
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Activation of the classical pathway of complement
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What is the main function of IgA?
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Mucosal immunity
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Where is IgA secreted?
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Into the mucosal secretions of the GI and respiratory tracts
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What are the 2 main functions of IgE?
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-ADCC via eosinophils
-Mast cell degranulation |
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What type of hypersensitivity is IgE involved in?
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Type I - immediate
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How do antibodies act to neutralize microbes and toxins?
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By binding to them and preventing them from entering infected cells, or from infecting neighboring cells once infected cells die and lyse.
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What is Opsonization?
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The coating of a microbe or toxin with a substance that promotes phagocytosis
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What is an Opsonin?
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The substance that promotes phagocytosis
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How do antibodies act as opsonins?
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By binding to microbes which leaves their Fc regions free to bind to Fc receptors on macrophages and phagocytes.
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When an Fc receptor of an Ab/Ag complex binds to a phagocyte, what is the response?
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1. Phagocytosis of the complex
2. Activation of the killing mechanisms within the phagocyte |
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Where in the body is the major site of phagocytosis of opsonized bacteria?
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The spleen
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So what are splenectomized patients susceptible to?
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Disseminated infections
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Against what type of pathogen is opsonization the major host defense mechanism?
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Encapsulated bacteria
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Are all Fc receptors on phagocytes the same?
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NO; they are different based on which isotype the Fc region is on.
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Can free/naked antibody cause opsonization?
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No; why would you want phagocytes to eat free antibody? It has to be crosslinked by microbe or toxin.
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What is the major bacterial phagocytosis Fc receptor?
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Fc-gamma-R1
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What cells express Fc-gamma-R1?
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-Macrophages
-Neutrophils -Eosinophils |
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What antibodies bind best to Fc-gamma-R1?
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-IgG1
-IgG3 -IgG monomer |
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What is the function of the Fc-gamma-R2B receptor?
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It is the receptor that binds IgG-antigen complexes to turn down the immune response - negative feedback inhibition of Bcells.
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What cells express Fc-gamma-R3A?
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NK cells
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What is the function of the Fc-gamma-R3A receptor on NK cells?
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ADCC
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What cells express Fc-epsilon-R1?
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-Mast cells
-Basophils -Eosinophils |
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What is the function of the Fc-epsilon-R1 receptor?
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Cell activation and degranulation
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ADCC is:
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-antibody
-dependent -cellular -cytotoxicity |
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What cells do the killing in ADCC?
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-NK cells
-Eosinophils |
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What is the Fc receptor on NK cells that allows for ADCC?
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Fc-y-R3A
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What is the Fc receptor on eosinophils that allows for ADCC?
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Fc-e-R1
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How is ADCC via NK cells stimulated?
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By the coating of a microbe with IgG, and binding of that IgG's Fc region to the FcyR3A receptor on the NK cell.
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What happens when NK cells are stimulated?
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They release their cytolytic granule contents.
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What are the cytolytic granule contents of NK cells?
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-Granzyme
-Perforin |
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When IgE coats parasites in helminthetic infections, to what cells do the IgE's Fc regions bind?
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Eosinophils
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What cytokine is produced by Th2 cells that stimulates eosinophil proliferation and activation?
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IL-5
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