Generation of leukemia-reactive cytotoxic T lymphocytes from HLA-identical donors of patients with chronic myeloid leukemia using modifications of a limiting dilution assay.

Abstract

Donor leukocyte transfusions (DLT) have an anti-leukemic effect in most patients with a relapse of chronic myeloid leukemia (CML) after allogeneic stem cell transplantation. However, DLT are often complicated by graft-versus-host disease. Selection of donor lymphocytes with a relative specificity for leukemic cells is desirable. The generation of leukemia-reactive cytotoxic T lymphocyte (CTL) responses between HLA-identical donors and patients in bulk cultures showed major variations, and false negative results were observed. In a modification of a limiting dilution analysis (LDA) two-fold serial dilutions of HLA-identical donor mononuclear cells (MNC) were cultured in the presence of CML cells. The anti-leukemic CTL precursor frequencies in these donors varied between <1 and 9 per 106 MNC. HLA-restricted CD4+ or CD8+ lymphocytes as well as MHC non-restricted gammadelta T cells were responsible for the anti-leukemic responses. A positive correlation between cytotoxicity in the various wells after 3, 4 and 5 weeks of culture could be found. The LDA may be superior to bulk cultures in selecting stable immune responses and in separating multiple different anti-leukemic T cell responses in each donor-patient combination.