Complement Notation C-----complement C1, C2, C3, C5 a-----small fragment C2a, C3a b-----large fragment C2b, C3b, csb activated (enzyme) C1 i---m-inactivated iC3b
Notation C-----complement C1, C2, C3, C5 a-----small fragment C2a, C3a b-----large fragment C2b, C3b, C5b ¯ -----activated (enzyme) C1 i-----inactivated iC3b Complement
Complement Activation of the complement system 1 Classical pathway 2, MBL pathway MBL: mannan-binding lectin 3. Alternative pathway
Activation of the complement system 1. Classical pathway 2. MBL pathway MBL: mannan-binding lectin 3. Alternative pathway Complement
Complement Classical pathway A suitable Ab bound to Ag, Ag-Ab complex C1, c4, c2 and c3, ca++ and matt cations 1 C1 activation 2. C4 and C2 activation(generation of C3 convertase) 3. C3 activation(generation of C5 convertase) 4 Generation of c5 convertase marks the end of the classical pathway
Classical pathway A suitable Ab bound to Ag, Ag-Ab complex C1, C4, C2 and C3, Ca++ and Mg++ cations 1. C1 activation 2. C4 and C2 activation (generation of C3 convertase) 3. C3 activation (generation of C5 convertase) 4. Generation of C5 convertase marks the end of the classical pathway Complement
STUDENT CONSULT Serum conc Protein ( g/mL) Function Initiates the classical pathway, C1q (C1qr2S2) binds to Fc portion of antibody; Clr and c1s are proteases that lead to C4 and C2 activation C4 300-600 C4b covalently binds to surface of microbe or cell where antibody is bound and complement is activated C4b binds to C2 for cleavage by C1s C4a stimulates inflammation C2 as an active enzyme of C3 andng C2b is a serine protease function C5 convertases @ElsevierAbbas&Lichtman:BasicImmunologyUpdated2e-www.studentconsult.com ownloaded from Student Consut (on 1 June 2006 04: 16 PM) 82005 Elsevit
Downloaded from: StudentConsult (on 1 June 2006 04:16 PM) © 2005 Elsevier
Complement Activators r Activation of this pathway may occur via Ag- Ab complex (immune complex, Ic) or by aggregated Ig. r IgG(IgG1, IgG3)and IgM are most efficient in reacting with complement. r Only one molecule of IgM is required, whereas at least two molecules of igg are needed r Soluble antibody cant activate complement
Activators Activation of this pathway may occur via AgAb complex (immune complex, IC) or by aggregated Ig. IgG (IgG1,IgG3) and IgM are most efficient in reacting with complement. Only one molecule of IgM is required, whereas at least two molecules of IgG are needed. Soluble antibody can’t activate complement Complement