Lecture 3 - Complement Flashcards
(21 cards)
where are the complement proteins made?
in the liver
what pathway is involved with adaptive immunity?
classical pathway
what 3 functions are involved in all complement pathways?
lysis of bacteria pathogen, promotion of phagocytosis and triggering of inflammation
what does C3 converts do?
converts C3a to C3b
what is the difference between C3b and C3a?
C3a is an inflammatory molecule yet C3b is deposited on the microorganism
how does C3b being deposited help the immune response?
helps opsonisation and phagocytosis
what does the C5-C9 cascade do?
forms the membrane attack complex for the lysis of the microorganism
what function does C5a convertase have?
triggers a cascade that forms the MAC
how does the lectin pathway begin?
MBL or ficolin binds to specific carbohydrates on the pathogen surface
how does the classical pathway begin?
C1q interacts with the pathogen surface or with the antibodies bound to the surface
how does the alternative pathway begin?
C3 undergoes spontaneous hydrolysis to initiate the deposition of C3 converts on microbial surfaces
how is the alternative pathway regulated?
by host cells
what are the 3 outcomes of activation?
C3a and C5a recruit phagocytic cells, phagocytes with receptors for C3b engulf the pathogen and formation of MAC
how does the inflammatory response allow molecules to travel through tight junctions?
C3a and C5a increase vascular permeability which allows fluid leakage from blood vessels, allowing migration of macrophages, PMNs and lymphocytes
where are complement control proteins at the highest concentration?
in the blood plasma
how are self cells avoided by complement?
on the surface of host cells are complement control proteins
what is an example of a complement control protein?
CD59 (protectin)
how does CD59 work?
inhibits C9 polymerisation during the formation of the MAC
how does C1 inhibitor work?
binds to C1 to prevent its activation in the classical pathway
what is decay accelerating factor?
bound to erythrocyte plasma membranes which inhibits C3 convertase action
what is the issue with innate activation of the complement system?
there are many genes that create proteins associated with complement regulation which can result in a loss of regulation and may cause hyperactivation causing immunocompromisation and autoimmune diseases
