Complement- Lecture 10/5/21 Flashcards
Complement
A series of proteins working in a cascading manner to generate defense mechanisms
Three different pathways of complement activation
- Classical
- Alternative
- Mannan binding ligand
C1q
First protein to bind to the Fc site of antibody, recruits C1r and C1s
What activated C1 cleaves
C4, making C14b
What C14b cleaves
C2, making C14b2b
What C14b2b cleaves
C3, making C14b2b3b
What C14b2b3b cleaves
C5
Membrane attack complex
C5b through C9
C9 function
Creates channel in the cell membrane to allow lysis
Complement proteins responsible for opsonization
C3b
C3a and C5a function
Chemotaxis and Anaphylatoxin production
Anaphylatoxins
Involved in Mast cell degranulation
C1-inhibitor
Important regulator of the primary pathway
Alternative complement pathway initiation
Factor B, D and properdin combine with residual C3b in blood in response to lipopolysaccharide creating C3bBbP, initiates membrane attack complex
Inhibitors of the alternative pathway
Factor H and Factor I
Lectin Pathway
Activated by organisms with mannose on their surface
Proteins important in Lectin Pathway (3)
- MBL
- MASP1
- MASP2
Absence of C1q, C2, or C4
Associated with SLE (lupus)
Absence of C3
Severe recurrent bacterial infections
Absence of C5
Bacterial infections, like C3 but not quite as bad
Absence of C6,7, and 8
Overwhelming Neisserial infections (N. Meningitidis, N. gonorrhea)
Absence of alternative/lectin pathway components
Recurrent bacterial infections
Absence of C1-INH
Hereditary angioedema
Hereditary angioedema
Autosomal dominant, episodes of angioedema without urticaria or pruritis, can lead to asphyxiation
