Etc. Flashcards
FcRn
Neonatal Fc receptor that transports Abs from the mom to the fetus. It protects IgGs from intracellular catabolism.
Types of Fc receptors (4)
FcyRI (CD64) - high affinity, phagocytosis and cell activation.
FcyRII (CD32) - low affinity, feedback inhibition.
FcyRIII (CD16) - low affinity, Ab-dependent cell-mediated cytotoxicity (NK cells only).
FceRI - high affinity, cell activation (mast cells)
Most efficient opsonization mechanism:
IgG3 and IgG1 binding FcyRI (CD64)
Polymorphism in FcyRIIB gene is linked to:
Systemic lupus erythematosus
Antibody-dependent cellular cytotoxicity (ADCC)
Ab binds FcyRIII on NK cells, caused cross-linking, NK kills target cell.
C5 convertase equals what in the alternative pathway?
C3bBb3b
C5 convertase equals what in the classical pathway?
C4b2a3b
CR1 (CD35) function
A high affinity receptor for C3b and C4b
Promotes phagocytosis and clearance of immune complexes.
CR2 (CD21) function
High affinity for C3d, C3dg and iC3b.
Enhance B cell responses.
How does EBV enter B cells?
Via CR2 and remains latent for life.
CR3 (Mac-1)
An integral that functions as a receptor for iC3b.
Also involved in the recruitment of leukocytes to infection.
CR4 functions similarly.
Factor I
Cleaves C3b and C4b.
Inhibition.
Factor H
Binds C3b and displaces Bb.
Cofactor for factor I.
MCP
Cofactor for factor I-mediated cleavage of C3b and C4b.
DAF
Causes dissociation of C3 convertase.
C1 INH
Terminated classical activation.
CD59 and plasma S protein
Inhibit MAC formation.
Microbes on which complement is activated become coated with what?
C3b, iC3b or C4b and are phagocytosed.
What complement fragments induce acute inflammation?
C5a, C4a, C3a.
C3d binds what on B cells?
CR2 (CD21)
C1q, C2 and C4 deficiencies are associated with:
SLE
C3, propirden, and factor D deficiency is associated with:
Pyogenic bacterial infections
C5, C6, C7, C8, C9 deficiencies cause:
Neisseria bacteria infections
what Igs does an infant have access to?
IgG from mom via placenta
IgA via brest milk
Transcytosis
Process of transports Abs from milk across gut epithelium.
First level of resistance to infections by infants depends on:
Activity of the phagocytic system.
Reasons IgG is most protective:
Higher acts in blood. binds avidly to Ag. Activates complement system. Good at opsonizing. Relatively small and penetrates easily to tissues.
Timeline of fetal Ab production
Some IgM is produced in utero.
IgG is produced at high levels after birth.
At 6 mo old, mom’s Abs are gone and newborns are on their own.
Tfh secrete what? Causing what?
IL-21 which is needed for GC development (isotype switching, affinity maturation, Ab production) and generation of plasma cells.
IFN-y or IL-4 which controls isotope switching.
Tfh express:
ICOS
PD-1
IL-21
Bcl-6
CD40 engagement induces:
AID
