Adaptive Immunity Flashcards
Immunology 2
The Acute Phase Response
involves changes in the plasma concentrations of specific proteins in response to inflammation
What drives acute phase response?
Pro-inflammatory mediators released by activated macrophages.
This is mediated by liver hepatocytes which produce a variety of acute phase proteins
Proteins of the complement system include…
- C3 and MBL (Manose Binding Lectin)
- C reactive Protein (CRP)
CRP is a …
major acute phase protein in humans,
used as a marker for inflammation &
functions as an opsonin to enhance bacterial cell phagocytosis
CRP role`
- Primes certain bacteria for destruction by the complement system & phagocytes
- Has a prognostic role (severity, duration)
What’s the complement system?
A system of reactions and proteins and molecules
that act to complement ongoing innate and adaptive immune responses
Central protein in complement system is…
C3 (Acute phase protein, produced in response to inflammation but usually present in body at low levels)
C3 is activated by…
multiple different mechanisms:
1. classical pathway
2. MBL pathway
3. alternative pathway
Proteolytic cleavage changes inactive C3 into active C3a and C3b subunits
What’s MBL?
Immune molecule that binds mannose (sugar found in cell wall of some bacteria) and is activated. It undergoes a conformational change which will allow it to bind to other proteins of the complement system, activating those which actiavtes a whole cascade of proteins. Eventually active enzyme complex is generated (C3 convertase) that splits and cleaves inactive C3 to produce active C3a & C3b.
C3b
-C3b in solution is very unstable.
-So in order to carry out downstream functions, it has to bind to surface of cell to complement inhibitors.
-C3b is an opsonin (binding to surface of bacterial or fungal cell, C3b is a flag to our phagocytic cells which also express receptors for C3b)
