Cytotoxic lymphocyte antigen-4 (CTLA-4) is a member of the immunoglobulin superfamily that is expressed on the surface of activated T cells and downregulates T cell function.1In the mid-nineties, theCTLA-4gene was reported as one of the important susceptibility genes in T1DM,2since that time, attentions have been made toward the exact role of this gene. The gene discussed is CTLA4; the disease is type 1 diabetes mellitus.