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Complement system & activation Dr.Ghada Boghdadi. Objectives: List the components of the complement system. Discuss the chemical composition of complement. Explain the role of host defense mechanisms. Explain the role of complement in disease process.
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Complement system & activation Dr.Ghada Boghdadi
Objectives: • List the components of the complement system. • Discuss the chemical composition of complement. • Explain the role of host defense mechanisms. • Explain the role of complement in disease process. • Describe the relationship between classical and alternate pathway. • Describe the consequences of complete activation. Anantha Narayanan Ch 15
1- Historically, the term complement (C) was used to refer to a heat-labile serum component that was able to lyse bacteria (activity is destroyed (inactivated) by heating serum at 56 degrees C for 30 minutes). 2- Complement comprises over 20 different serum proteins that are produced by a variety of cells including, hepatocytes, macrophages and gut epithelial cells. 3- Complement term refers to the ability of these proteins to complement the effects of other components of the immune system. 4- Complement proteins circulate in the blood in an inactive form. 5- Their activation sets in motion a domino effect (complement cascade).
* C1(qrs), C2, C3, C4, C5, C6, C7, C8, C9. * factors B, D, H and I, properdin (P). * mannose binding lectin (MBL), MBL associated serine proteases (MASP-1 MASP-2)
Biological effects: • 1- Opsonization to enhance phagocytosis. • 2- Phagocyte attraction and activation. • 3- Lysis of bacteria and infected cells. • 4- Regulation of antibody responses. • 5- Clearance of immune complexes. • 6- Clearance of apoptotic cells.
C1r C1s C1q Ca++ Components of the Classical Pathway C4 C2 C3 C1 complex
MBL Components of mannose-binding lectin pathway C4 MASP2 C2 MASP1
Components of thealternative pathway D C3 B P
The Lytic pathway Generation of C5 convertase leads to the activation of the Lytic pathway
C8 C7 Components of the lytic pathway C6 C5 C 9
Regulation of the complement system 1- C1 inhibitor 2- H & I factor 3- Decay-accelerating factor (DAF)