RCA-I binding on platelets co-cultured with CD8+ T cells from ITP patients in the cytotoxic group was significantly increased compared with those co-cultured with CD8+ T cells from the non-cytotoxic group and controls (RCA-I binding ratio: cytotoxic vs. non-cytotoxic, 1.59 ± 0.41 vs. 1.17 ± 0.34, respectively, P < 0.001; cytotoxic group vs. controls, 1.59 ± 0.41 vs. 0.94 ± 0.27, respectively, P < 0.001). This evidence concerns the gene CD8A and autoimmune thrombocytopenic purpura.