This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Immunology, Subject name: Microbiology
The HLA class-III region genes are impoant elements in 
Select and explain. 
A. Transplant rejection phenomenon, B. Complement system, C. Immune surveillance, D. Antigen presentation and elimination.
B: Complement system
Answer: B: Complement system 
Explanation: HLA class III region contains genes that encode several components of the complement system (i.e. C2, C4a, C4b, Bf), they are responsible for the levels of components of the complement system. In addition to components of the complement system, MHC III genes code inflammatory cytokines, tumour necrosis factor a and 0 (TNF a and P), two heat shock proteins (HSP) Ref : Ananthanarayana textbook of Microbiology 9th edition Pgno : 140