2. COMPLEMENT BASICS
Cooperate with antibodies to eliminate bacteria,
viruses, and other pathogens
A complex group of about 16 different plasma
proteins that work together to lyse their targets
Prevent the lysis of normal host cells by
pathogens
It operates as a cascade mechanism, just like the
blood-clotting system
This sequential activation usually occurs by
proteolysis
3. COMPLEMENT BASICS
• Amplification
• Factors produced by liver as zymogens
• Different pathways converge onto C3
• C3 is complement factor of highest serum
concentration (1.2 mg/ml)
• Complement proteins account for 10% of
serum proteins(3-4g/l)
4. It ensures a
substantial
amplification of an
initial response.
This pathway can be
fairly easily
controlled in its
early stages by
inhibitors of
enzymatic activity.
•Since each successive
component of the
complement system is an
enzyme that can act on many
different substrates, this
system of successive
enzymatic steps gives a great
increase in the size of the
response.
•This is essential because the
C (complement) system is, as
we’ll see, very destructive,
and if it could be activated
easily and spontaneously, it
would cause considerable
harm to the organism.
27. Hereditary angioneurotic edema
Deficiency of C1INH
Autosomal dominant
Recurrent episodes of
edema in the skin, GI
tract, UG tract, and larynx
Abdominal, pelvic pain,
suffocation
Type I AND Type II
28. Paroxysmal nocturnal hemoglobinuria
Intermittent intravascular hemolysis
Defect of both CD59 and DAF (Glycosyl phosphatidyl inositol
anchored proteins)
Pig-A gene on X chromosome is involved
Alternate pathway is activated on host erythrocytes which
leads to hemolysis
Characterized by hemolysis,pancytopenia and venous
thrombosis
Death occurs due to hepatic vein thrombosis and bone
marrow dysfunction
