CTLA-4 A49G Polymorphism and Autoimmune Blood Diseases.

The cytotoxic T lymphocyte associated antigen-4 (CTLA-4) is expressed on T lymphocytes, and inhibits the T cell responses. CTLA-4 A49G polymorphism was found to be associated with various autoimmune diseases in recent studies. In this study we evaluated the frequency of CTLA-4 A49G polymorphism in patients with autoimmune hemolytic anemia and autoimmune thrombocytopenia. One hundred and fifty healthy Turkish subjects, 46 patients with autoimmune hemolytic anemia (AIHA) and 62 patients with autoimmune trombocytopenic purpura (ITP) were included to our study. In healthy controls; genotype frequencies were 48% for AA, 47.3% for AG and 4.7% for GG. A-allele frequency was 71% and G allele frequency was 29%. Allele frequencies were similar to the other European countries. In AIHA group; 21 patients had AA (45.6%), 21 had AG (45.6%), and 4 had GG (8.8%) genotype. A allele frequency was 68.4%, and G allele frequency was 31.6% which are similar to healthy controls. In ITP group; 38 had AA (61.3.%), 21 had AG (33.9%), and 3 had GG (4.8%) genotype. A allele frequency was 78.4 %, and G allele frequency was 21.6%. We found no difference between ITP patients and controls for CTLA-4 A49G polymorphism. In subgroup analysis however, we found that all CLL patients with AIHA had CTLA-4 A49G polymorphism (3 had AG, 1 had GG). This may suggest that CTLA-4 A49G polymorphism is an important risk factor for the development of AIHA in CLL patients. Further genetic and clinical studies are required to understand the exact role of CTLA-4 A49G polymorphism in the development of autoimmune diseases.