This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Auto Immune Disorders Introduction, Subject name: Pathology
Autoimmunity is caused by all of the following, except: 
Select and explain. 
A. Infections, B. Expression of cryptic antigens, C. Negative selection of T-cells in the thymus, D. Inappropriate expression of the MHC proteins
C: Negative selection of T-cells in the thymus
Answer: C: Negative selection of T-cells in the thymus 
Explanation: Infections- Infections like EBV and HIV cause polyclonal B-cell activation, which may result in production of auto-antibodies. The tissue injury that is common in infections may release self-antigens and structurally alter these antigens so that they are able to activate T cells that would not be tolerant to these new, modified antigens. Expression of cryptic antigens - Classically seen in patient suffering from Rheumatic Fever. Cryptic or hidden antigens will be exposed as there will be inflammation caused by the cells and that is responsible for causing Autoimmune disease. Negative selection of T- cells:-Protective against development of Autoimmune disease. (negative selection of self-reactive T cell reduces the risk of autoimmune disease.) Inappropriate expression of the MHC proteins