Cytotoxic T lymphocyte antigen-4 (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. In animal models, it has been shown that complete CTLA-4 deficiency was lethal due to massive infiltration of tissues by polyclonally proliferating lymphocytes. CTLA-4 A49G polymorphism, which has been suggested to reduce the inhibitory function of the CTLA-4 molecule, 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 46 patients with autoimmune hemolytic anemia (AIHA), 62 patients with immune thrombocytopenic purpura (ITP), and 150 healthy individuals.

Allele frequencies and genotype distributions were similar in both ITP and AIHA patients compared to healthy individuals. In subgroup analysis, however, we found that in chronic lymphocytic leukemia (CLL) patients with AIHA (n=4), all patients had CTLA-4 A49G polymorphism (3 had AG, 1 had GG). There was no significant statistical association between G allele and systemic lupus erythematosus (SLE) or AIHA.

These data suggest that CTLA-4 A49G polymorphism does not contribute to the pathogenesis of lymphoproliferative diseases itself, nor does it increase the risk of autoimmune complications in patients with lymphoproliferative disease.