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29 Cards in this Set
- Front
- Back
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What are the 4 main functions of Abs?
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1) Neutralization
2) opsonization and phagocytosis 3) Ab-dependent cellular cytotoxicty 4) complement activation - lysis, phagocytosis, inflammation |
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What does IgG do?
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- neutralization
-opsonization - activates classical pathwaay of complement - ADCC by NK cells - Neonatal immunity - Feedback inhibition of B cell activation |
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What does IgM do?
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- activates classical pathway of complement in blood
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What does IgA do?
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- Mucosal immunity
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What does IgE do?
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- helminths defense
- mast cell degranulation |
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What are the 3 scenarios given that Ab prevents by neutralization?
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- initial infection of cells/tissue
- prevents spread of infection - prevents toxins from binding to cellular receptor |
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The FcyRI is on what types of cells and does what? what type of Ig?
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- macrophages, neutrophils, eosinophils
- phagocytosis - high affinity IgG |
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The FcyRIIB is on what cell and does what? what Ig?
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- B lymphocytes
- feedback inhibition of B cells - Low affinity IgG |
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The FCyRIIIA is on what cells and does what? what Ig?
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- NK cells
- ADCC - low affinity IgG |
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The FceRI is on what cells and does what? What Ig?
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-- mast cells, basophils, eosinophils
- against helminths - High affinity IgE |
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What are the early steps of the classical pathway of Complement activation?
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- Binding of IgM/IgG to microbial Ag changes conformation
- C1 binds - C4/2 mimic C3 - starts process to increase C3b opsonization |
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What are the early steps of the lectin pathway for complement activation?
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Innate
- Mannose binding lectin binds to mannose and initiate pathway to tag microbe with C3b |
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What are the early steps of the alternative pathway for complement activation?
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(innate)
- C3 spontaneously hydrolyzed - C3b binds to microbe and is stabilized - continues and microbe is covered with C3b |
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What C protein initiates the classical pathway?
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- C1
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Why is IgM a better activator of the complement system?
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- b/c IgM is a penter, only 1 IgM is necessary to bind to a single C1
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What are the late steps in complement activation?
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- C5 activates the rest of the C (6,7,8) and C9 forms MAC
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What are the 6 main functions of the complement system?
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1) opsonization/phagocytosis
2) complement-mediated cytolysis 3) stimulates inflammation 4) binding C3d to B cell CR2 is a second signal for humoral 5) increases binding of Ag-Ab-C to FDC which is involved in selection of high-affinity B cells 6) Tags Ag-Ab complexes to be removed in the spleen/liver |
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What complement proteins of the classical pathway cause immune complex disease when defective?
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- C1
- C4 - C2 - C3 |
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What happens when C5/6/7/8/9 are defective?
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Disseminated Neisserial infection
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Why doesn't the complement system attack our own cells?
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Mammals have regulatory proteins to prevent this
- Membrane regulatory proteins ------DAF: terminates alternative and classical - Plasma regulatory proteins -----C1 inhibitor: prevents assembly of C1 complex |
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What are 2 ways that the complement system is regulated?
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1) DAF gets close to C3B and doesn't let anything else bind
2) C1-INH binds to C1r2s2 (2 portions of CI) so C1 complex doesnt form |
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What types of Ig are transferred via neonatal immunity?
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- IgG from placenta
- IgA from breast milk |
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What do microbes bind to when they infect the mucosa? What occurs from this?
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- M cells
- M cells are endocytosed to the MALT - DC processes Ag, presents to naive CD4 - CD4 activated so expresses CD40L and can bind to B - B cell mainly produces IgA |
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Why is IgA produced in the mucosa?
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- T cells secreting IgA cytokines (TGF-Beta)
- DC secrete IgA cytokines |
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What dimerizes IgA?
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- J chain within the lamina propria
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What is the FC receptor for IgA called on the mucosal epithelial cell?
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- Poly-Ig receptor
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How does IgA get into the lumen of the mucosal tract? (respiratory/gut)
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- binds to the Poly-Ig receptor
- endocytosed - within cell there is proteolytic cleavage of peptide |
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What is the receptor that enables IgG to enter the tissue from the blood?
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- FcRn
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What happens when there is a defect in C3?
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- fatal early in life
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