BIOB11H3 Lecture Notes - Lecture 5: C1 Complex, Lectin Pathway, Complement System
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Thursday, September 26, 2019
Biol 3120 - immunology
-The complement system!
•inﬂammation: lessening the blood vessel linings, some of the signalling molecules
excreted by the tissue in the blood stream and it goes to the liver to induce an
increase of responses from the liver. Components secreted by the liver is always
•Complement proteins can be put into 7 diﬀerent categories!
•Once a complement pathway is induced an irreversible chain of reaction occurs
until a product is produced. !
-Opsonins: coat pathogens and interact with phagocytes to initiate a rxn!
-Some complement proteins are receptors: on cellular surface!
-Regulator proteins: regulating of the immune system!
•Iniatiator starts of the process and it can go down in one of 3 pathways!
•Classical are lectin are initiated diﬀerently but comes together as one complex!
•C1 complex: initiator. It can only initiate the pathway when the C1 makes
contact with an anti-body (part of the adaptive immune response).!
•IgG and IgM (come from the b-cell receptor)!
•IgG is secreted as a monomer!
•When antibody makes contact with an antigen (it changes conformation).
Limits accidental initiation of the pathway!
•IgM: secreted as a pentamer. Multiple antibody - antigen contact to initiate the
C1 complex (capable of initiating inﬂammation response)!
•C1 can cleave c4 ﬁrst and then C2(only one that’s backwards?)!
•convertase: cleaves complements!
•Makes 2 convertases:!