Question

A patient is deficient of the complement protein C3. Describe one effect this deficiency could have on inflammation.

Answer 1

Answer: Complement system is the part of innate immune system however also helps in adaptive immunity (antibodies functions). It enhances the ability of antibodies, phagocytic cells to clear pathogen and damaged cells through promoting inflammation and attacking on the cell membrane of the pathogens. Approx 30 different protein and protein fragments are the part of complement system. C3 is one of them. Complement system have three different pathways (Classical pathway, Alternative pathway and Lectin pathway) for the generation macrophage activation complex (MAC). C3-protein is an intermediate of all three pathways. The activated C3 convertase (activated from all the three complement pathways) acts on C3-protein and break into C3a and C3b. C3a is smaller fragment contains anaphylatoxin activity (promoter of acute inflammation). The C3a binds with mast cells and induce the degranulation of mast cells, increase the vascular permeability and smooth muscles contraction that all results into heighten inflammation. In absence of C3-protein C3a is not generated by C3 convertase and further due to lack of C3a individual is insufficient of inflammation. So in patients with deficient of C3 protein having insufficient or lack of inflammation.