CD4 and thrombotic thrombocytopenic purpura: In studies on thrombotic thrombocytopenic purpura (TTP), several T-cell peptides were identified in ADAMTS13 (Table 4), with the ADAMTS13 1239-1253 peptide (GDMLLLWGRLTWRKM) as the single immunodominant CD4+ T-cell epitope that was bound both by HLA-DRB1*15:01 and DRB1*11:01 in ELISA and also by T-cells from a strain of mice expressing human HLA-DRB1*01:01 (104).