HLA-DRB1 and chronic myelogenous leukemia, BCR-ABL1 positive: Thus, it has been shown that the CD4+ T cells responding to exposure to p210bcr-abl-derived peptides in a HLA-restricted manner did not exhibit cytotoxic activity [27] and that CD4+ T cell clones isolated from healthy HLA-DRB1 individuals and reactive with p210bcr-abl-derived peptides paradoxically enhanced the number of CML cell colonies when cocultivated with CML cells obtained from HLA-DRB1 positive patients [28].