Sarfaraz Alam
+91-9473561898
sarfarazalam408@yahoo.com
www.sarfarazalambms.blogspot.com
Institute of Biomedical sciences
C was discovered several years ago as a heat labile
of normal plasma that augment opsonozation of
bacteria by Ab.coplement the antibacterial activity
of Ab
Consist of approximately 30 serum molecules
10% of the total serum proteins
One of the major defense system of the body
Control of inflammatory reaction and chemotaxis
Clearance of the immune complexes
Cellular activation and antimicrobial defense
It is a major effector in immuno-pathological diseases
C1(C1q, C1r, C1s ) factor B
C2(C2a, C2b) factor D
C3(C3a, C3b) DAF, CD55
C4(C4a, C4b) CR1,CD35
C5(C5a, C5b) factor H
C6 factor I
C7
C8
C9
1-classical pathway which is activated by Ab bound to
Ag
2-the lectin pathway activated by carbohydrates
3-Alternative pathway activated in the presence of
various microbial pathogen
The protein of the system act in enzyme cascade
1-it generate large numbers of activated complement
proteins that bind covalently to pathogens, opsonizing
them for engulfment by phagocytes bearing receptors for
complement
2-the small fragments of some complement proteins act as
chemo-attractants to recruit more phagocytes to the site of
complement activation and also to activate these
phagocytes
3-the terminal complement components damage certain
bacteria by creating pores in the bacterial membrane
C1q bind to Ab complexed
with Ag
C1q can also bind directly
to the surface of some
pathogenes
C1q bind to 2C1r and 2C1s
zymogene
Binding of C1q heads to the
pathogene surface cause
enzymatic acivity of C1r,
then cleave C1s to generate
serine protease
The α chain of C3 and C4
contain a thioester bond
between cystein and a
glutamine, fallowing
cleavage to C3a & C3b
,allowing C3b or C4b to
form covalent bond with
protein and carbohydrate