what activates the
classic complement pathway
(IgG or IgM binds antigen and then C1 coimplement protein)
what activates the alternative pathway?
- activated by molecules on the surface of microbes
- spontaneous activation
DOES NOTrequire antibodies
lectin pathway in complement cascade
needs what to activate it
Microbial surfaces (mannose)
Mannose-biniding lectin binds mannose on surface of microbes
what is the starting point of the CLASSIC PATHWAY
C1 inhibitor inhibits (esterase inhibitor) cleavage of C1 into active components
membrane attack complex
is formed by
this causes phagocytosis of encapsulated bacteria
if a pt is def in C3b what infections are the suceptable to?
what are the two most important opsonins
C3b and IgG
C3a, C5a and C4a
stimulate what cells
deficiency of C1 esterase inhibitor
causes what disease?
- due to unregulated activation of kallikrein --> inc bradykinin
classic findings: edema of skin (especially periorbital) + mucosal surface
CI: never give ACE inhibitor
Deficiency of C3
can lead to?
recurrent pyogenic sinus infections and respiratory tract infections.
(especially encapsulated bacteria)
- strept pneumoniae, H. influ
**inc susecptibility to type III hypersensitivity rxn
-especially ( glomerulonephritis)
def of C5b, C6, C7, C8 or C9 (MAC)
cant form Membrance attack complex.
this incresaed risk for?
( gonoccocal or meningococcal)
def in DAF (CD55)
.paraoxysmal nocturnal hemoglobinuria
occurs when RBCs are def in two surface molecules that help protect against the MAC:
-Glycoylphospnoinositol (GPI) which anchors decay accelerating factor (CD55) to plasma membrane
- MAC- inhibitory protein (CD 59)
get chronic intravascular hemolysis-->
- thrombosis (platelets get destroyed releasing prothrombotic contents)
diagnosis - hams test (lysis rbc at low ph), flow cytometry - look for CD55/59. if not seen then they have it
TX - transfusion, warfarin, ECULIZUMAB.