Humoral Immunity Flashcards
which Ig is main defense in saliva, which cells produce it, and how do they act
IgA, plasma cells produce IgA in salivary glands and inhibit attachment of oral species to epithelial cells
what are the three function of antibodies or Ig that don’t involve complement system
- neutralization of microbes and toxins
- opsonization and phagocytosis of microbes
- antibody-dependent cellular cytotoxicity (ADCC)
what are the three function of antibodies or Ig that use complement activation
- lysis of microbes
- phagocytosis of microbes opsonized with complement fragments
- inflammation
which region(s) of Ig is needed for neutralization
variable region
which region(s) of Ig is needed for elimination
variable and constant region
both neutralization and elimination are triggered by what:
binding of antigen to variable regions
what kind of antibodies are the most effective
antibodies with high affinity for antigens
IgG is generally found where
blood
IgA is generally found where
mucosa
for neutralization, binding molecules on microbes required for infection cells/tissues does what
blocks colonization
antibody binding microbes can stop it from doing what two things
passing through epithelial barriers, and binding to individual cells to infect them
T/F antibody can bind to toxins and block binding to cellular receptor
True
what does FcR bind
constant region of Ig
what happens to FcR that results in cellular activation
FcR clustering
clustering of FcR requires recognition of what
multivalent antigen by Ig
FcyRI/IIA promotes what
phagocytosis of Ig-coated microbes by phagocytes (IgG)
FcyRIIIA (CD16) induces what
killing of Ig-coated infected cells by NK cells (ADCC)
FceRI induces what
degranulation of mast cells (IgE)
what is meant by multivalent antigen
antigen that can bind multiple Ig
how is helminth killed
- FceRI binds Fc portion of IgE-coated helminth
- triggers degranulation of toxic mediators that kill helminth
do FceRI and IgE target infected cells when killing helminth?
nope. do not target infected cells
which cells are coated with IgE specific for allergens, and with FcR is involved
mast cells and basophils
FceRI
what happens to FceRI that is bound to IgE by multivalent allergen that triggers degranulation
clustering of FceRI
activation of complement involves what
the sequential proteolysis of proteins to generate enzymes (zymogens)with proteolytic activity
products of complement activation covalently bind what:
-microbial surface
- Ab bound to microbes
- Ab bound to tissues
in the complement pathway, plasma proteins are activated by what
microbes
what does the complement pathway result in
phagocytosis, inflammation, and destruction of microbes
mammalian cells express proteins that block what
block complement fixation and subsequent activation
what are the three complement pathways
- classical
- alternative
- lectin
what is the alternative pathway triggered by
C3b binding to microbial surfaces
how do Factor D and Factor B interact in alternative pathway
Factor D cleaves Factor B
what does Bb do in alternative pathway
an enzyme able to cleave C3 into C3 and C3b
what is C3b also known as
opsonin
what is C3a also known as
anaphylatoxin (leukocyte recruitment and activation)
what is classical pathway triggered by
binding of C1 to microbe-bound antibodies (IgG, IgM)
what is the first component of the MAC (membrane attack complex)
C5b
what is the lectin pathway triggered by
binding of circulating lectins (MBL) to microbe polysaccharides (mannose)
what is the most important step in complement activation
cleavage of C3 by C3 convertase
what is the net result of the complement pathway
coating of microbes with C3b (opsonin)
what is the late step of the complement pathway
formation of the membrane attack complex (MAC)
which proteins are involved with the MAC
C5b, C6, C7, C8 and C9
what specifically does C9 do
multiple C9 form a pore - this causes osmotic swelling because H2O rushes into the cell
which microbe is especially susceptible to the MAC and why
Neisseria due to thin cell wall
how is complement activation regulated
plasma and membrane proteins prevent complement fixation at the surface of mammalian cells
what are the three general function of the complement system
- opsonization and phagocytosis (C3b protein)
- complement-mediated cytolysis (MAC causes osmotic lysis of microbes)
- stimulation of inflammatory reactions (anaphylatoxins)
which anaphylatoxin is most potent
C5a
then C3a, then C4a
what do the anaphylatoxins increase
extravasation (movement of WBCs into tissues) of plasma proteins and monocyte/neutrophils
- which leads to increase in microbicidal activities
