Immunology - 16 Flashcards
In complement, which are the anaphylotoxins the produce inflammation?
c3a, c4a, c5a
These a’s don’t float away, they have a function, others float away.
What is the function of the anaphylotoxins?
- Promote inflammation
- interact with receptors expressed on different cell types: vascular endothelial cells (activate and increase vascular permeability), neutrophils (activate, they leave circulation and go into tissue, follow the anaphylatoxin breadcrumbs which act as chemo attractants)
Which immunoglobulin isotypes activate the classical pathway?
IgM
IgG
Adaptive or innate immunity?
Adaptive
How many Fc regions that are bound to antigen are bound to C1 during the complement cascade?
2 Fc regions (2 antibodies)
Describe the classical pathway?
C1 -> C4 -> C2 -> C3 -> C5-C9
- c1 binds 2 Fc’s of antigen-antibody complex to activate c1
- c1 cleaves c4 (c4b binds to pathogen, 1st instance of zymogen)
- c1 cleaves c2 (c2a binds c4b on the pathogen, exception of b usually binding)
- c4b2a cleaves c3 (also called c3 convertase)
- c4b2a3b cleaves c5 (also called c5 convertase)
- c5b binds to the pathogen’s surface (1st step in MAC formation)
- c6, c7, c8 and multiple c9s join c5b to form the MAC (c5b6789n)
All complement pathways converge on which step?
c5b binds c6, initiating the formation of the membrane of the complex
Is the alternative pathway a part of the innate or active immunity?
Innate. So it is always on, not activated by antibodies. Activated by spontaneous cleavage of c3 (c3 binds to pathogen - cell wall components, LPS, cobra venom, viruses)
Which are the anaphylatoxins and which is the opsonin?
- anaphylatoxins (inflammation) - c3a, c4a c5a
* opsonins (opsonization) - c3b, c4b
How is complement inhibited (regulation)?
- Inhibit activation of the classical pathway (c1 inhibitor = C1INH controls cleavage of c4)
- inhibit c3 (degradation of c3b if it does not bind cell surfaces)
- inhibit MAC (protectin binds c5b678 and prevents recruitment of c9)
