DR Medhat MRCP

Complement system
o It`s a group of plasma proteins that play an important role in inflammatory & immune
responses.
Functions of complement system :
1. Recruitment of inflammatory cells.
2. Cellular activation.
3. Opsonisation &Cell lysis.
4. Antimicrobial defence.
5. Clearance of immune complexes.
6. Amplification of immune response .
Activation of complement system(3 ways) :
a) Classical pathway : - It`s activated by immune complexes.
- It`s initiated by binding of C1q to the Fc portion of Ig.
b) Alternative pathway : - occur either spontaneously in the fluid phase or on foreign
Activator (pathogen) surface.
- It`s initiated by C3 activation
c) Lectin pathway : - Initiated by Mannose-binding Lectin(MBL) & its associated serine
protease (MASP)
- Activates C4.
8. The activation of C3 is central event in activation of both classical & alternative pathway
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