Test 2: Antibody and Effector B cell Functions Flashcards
What antibody do plasma cells produce in salivary glands?
IgA
(also lots of IgG)
What are the functions of antibodies and Ig?
- neutralization of microbes and toxins
- opsonization and phagocytosis of microbes
- antibody-dependent cellular cytotoxicity
- lysis of microbes
- phagocytosis of microbes opsonized with complement fragments
- inflammation
- complement activation
What is the role of the variable region in humoral immunity?
neutralization
- triggered by binding of antigens to variable regions
What is the role of the constant region in humoral immunity?
elimination
- triggered by binding of antigens to variable regions
For neutralization of microbes, what is binding molecules on the microbes required for?
infecting cells/tissue blocks colonization
Which antibodies are the most effective?
antibodies with high affinity
What clustering of FcR require?
recognition of multivalent antigen by Ig
What’s the function of Fcy/RI/IIA?
promotes phagocytosis of Ig-coated microbes by phagocytes
What’s the function of FcyRIIIA (CD16)?
induces killing of Ig-coated infected cells by NK cells
(cytotoxicity)
What’s the function of FcERI?
induced degranulation of mast cells and basophils/eosinophils
How does antibody-dependent cell mediated cytotoxicity work?
NK cells bind IgG-coated cells via FcyRIII (CD16)
How does IgE and eosinophil-mediated killing of helminth work?
- FcERI binds FC portion of IgE-coated helminth
- triggers degranulation of toxic mediators that kill helminth
- does not target infected cells
What is used for the classical complement pathway?
C4b2a–> C4b2aC3b
(lectin pathway follows)
What is used for alternative complement pathway?
C3bBb–> C3bBbC3b
What is the result of 3 major pathways of complement activation?
results in phagocytosis, inflammation, and destruction of microbes
What are the early steps of the alternate complement pathway?
- triggered by binding of C3b to microbial surfaces
What are the early steps of the classical complement pathway?
- triggered by binding of C1 to microbe-bound antibodies (IgG, IgM)
What are the early steps of the lectin complement pathway?
- triggered by binding of circulating lectins (MBL) to microbe polysaccharides (mannose)
What is the most important step of complement activation?
cleavage of C3 by C3 converts which results in the coating of microbes with C3b for opsonization
What is the late step-membrane-attack complex?
- late step results in formation of membrane attack complex (MAC)
- MAC= C5b, C6, C7, C8 and multiple C9 that form a pore
- Neisseria susceptible due thin cell wall and allows pore to do damage
What is the function of the complement system?
- opsonization of microbes by C3b induces their phagocytosis
What is important for Neisseria infection?
MAC due to thin well and pore damage
