This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pathology
The HLA class III region genes are impoant elements in - 
Select and explain. 
A. Transplant rejection phenomenon, B. Governing susceptibility to autoimmune disease, C. Immune surveillance, D. Antigen presentation and elimination
B: Governing susceptibility to autoimmune disease
Answer: B: Governing susceptibility to autoimmune disease 
Explanation: Responses of MHC molecules Class I MHC class I molecules bind and process peptide that are derived from proteins synthesized within the cells, e.g. viral protein in viral infected cells and antigen of cancerous cells. These cells (cancerous or virus infected) have a tendency to display unusual, non self antigens on their surface After binding to MHC-I, these antigens are processed and presented to cytotoxic CD-8 T cells (MHC-I restricted). Cytotoxic CD-8 T cell - MHC I reaction cause - Graft rejection Cell mediated cytolysis of viral infected or tumor cells. Class II Class II molecules present exogenous antigen (e.g. extracellular microbes, soluble proteins). These antigens are first internalized and undergo proteolytic cleavage in lysosome. Peptide generated from this proteolytic cleavage are presented by MHC - II to CD4-T cells (MHC-II restricted) Reactions are Graft versus host response Mixed leukocyte reaction Class III "The MHC class III region contains many genes that are good candidates for the involvement in autoimmune disease". Recent data suggest that quantitative and qualitative diversities of the MHC III linked C4 among different ethnic groups can be impoant in susceptibility to autoimmune disease like SLE. Also Know The pa of MHC complex that code for TNF alpha & Beta and heat shock protein, is also referred as class IV MHC. -