Role of A49G polymorphism in systemic lupus erythematosus and its geographical distribution.

CTLA-4 (cytotoxic T-lymphocyte-associated protein-4) or CD152 is an inhibitory receptor expressed constitutively on CD4+ CD25+ T regulatory lymphocytes and transiently on activated CD4+ and CD8+ T lymphocytes. Its inhibitory function promotes long-lived anergy in immune cells and prevents autoimmunity. Therefore, it plays a crucial role in T cell-mediated autoimmunity, and thus in susceptibility to autoimmune diseases, including systemic lupus erythematosus (SLE). It is encoded by gene in humans. AtoG polymorphism at position +49 of gene is the only polymorphism which changes amino acid sequence from alanine to threonine in the leader sequence, which may affect the function of CTLA-4. Association of polymorphisms with SLE has been investigated in several reports in different ethnic populations from different countries, which have shown highly inconsistent findings. In this review, we have compiled previous studies which have reported the association of A49G polymorphism in SLE and its geographical distribution.