complement system 1 Flashcards
what do heat labile factors do
cause immune cytolysis
- C1, C2…
- promotes immune protection by short lived, enzymatic, inflammatory mediators
what happened when components are inserted into circulation
signalling agents interact initiating a cascade events
describe the complement cascades
- subsequent cleavage of proteins which is self amplifying
- 3 initiation mechanisms which converge
- efficient but complicated
what is the alternative pathway
- allows direct lysis of microqogransims in the absence of antibodies
- cascade starts with cleavage of C3
- pathways converge on the production of MACs allowing pathogenic cell lysis
where does C3 turnover occur
plasma and lymph
describe C3 turnover
C3 + H20 —–> C3H20 ——> C3OH
1) cleaves thioester bond
2) rapidly inactivates
what does the 3D structure of a protein determine
binding capacity and therefor function
what can affect a proteins 3D structure
- additional molecular markers
- binding of another protein
- change in environment
what does amylase do
break down starch
what does protease do
breaks down proteins
what does DNA methyltransferase do
transfers methyl to DNA groups
what does monoamine oxidase do
oxidises monoamines
what dies C3 initiation convertase do
catalyses the initial conversion of C3 into breakdown products
describe the process of C3 initiation convertase production
1) factor B and D association with C3H20
2) proteolytic cleavage forming Ba and Bb
3) factor D and Ba dissociation
4) production of C3H20Bb - C3 initial convertase
describe the process of C3b production
- C3 binds to C3 initiation convertase
- cleavage of C3 to C3a and C3b
- C3H20Bb continues cycle while C3b binds with factor B and factor D
- factor B splits into Ba and Bb and Ba is released
- C3 then binds to C3bBb + factor D
- C3a , C3b and C3H20Bb is produced
what is C3BbD
enzyme that cleaves C3 to C3a and C3b
how is C3b stabilised
opsonisation where it binds to the surface of microbes tagging them for phagocytosis
how is C3b degraded
- factor H binds to C3b which displaces Bb and releases it
- factor I then binds to C3b and factor H which forms iC3b
how is C3bBb stabilised
binds to microbial surface and properdin which protects it from factor H and I
what des C3bC3bBbP do
- is a C5 converts
- cleaves to C5 turning it into C5a and C5b
- C5a is released
- C5b, C6,C7,C8 and C9 recruited
how is a membrane attack complex formed
composed of C5b - C9
- C8 is inserted and disrupts the bacterial membrane and recruits C9
what is a membrane attack complex
forms a pore channel which causes osmotic lysis of the pathogen
what is affinity
the ending strength of a single binding site and its ligand
what is avidity
the total binding strength of a multivalent receptors with multiple epitopes
