BONE-MARROW-DERIVED T-CELL CLONES OBTAINED FROM UNTREATED ACUTE MYELOCYTIC-LEUKEMIA EXHIBIT BLAST DIRECTED AUTOLOGOUS CYTOTOXICITY

The eradication of minimal residual blast populations by activation of autologous cytotoxic cells with interleukin 2 (IL-2) is a new promisi ng tool in the treatment of acute myelocytic leukemia (AML). However, the immunological effector cells are not yet clearly defined. The pres ent study was designed to investigate the presence of cytotoxic precur sor cells in active AML and to identify phenotypical and functional ch aracteristics of autologous anti-leukemic cytotoxic effector cells. Fo r this purpose, mononuclear cells (MNC) containing at least 70% leukem ic blasts were isolated from bone marrow of untreated AML and cultured in the presence of 3000 IU/ml recombinant IL-2 (rIL-2) for 6-8 weeks. Under these conditions, T-cells were selected in the bone marrow cult ures and overgrew the leukemic blasts. The resulting T-cell population s were cloned by limiting dilution and the clones obtained were charac terized for their phenotypical and functional patterns. Totally, cloni ng resulted in 68 clones and a few cell lines. The clonality was verif ied by RT PCR analysis of TCR V beta gene expression. All clones obtai ned stained positive for CD2, CD3, DR and CD56. The vast majority (68% ) of T-cell clones/lines was CD4(+), a few clones expressed CD8 (19%) or CD4 and CD8, and four clones were of TCR gamma delta origin. Seven of 15 clones tested, including three CD4(+), two CD8(+) and two TCR ga mma delta(+)-clones were found to be cytotoxic against autologous leuk emic blast cells. All except one clone expressed oncolytic activities against allogeneic blasts too. One of the TCR gamma delta(+)-clones de monstrated NK activity by lysis of K562 targets. The majority of the T -cell-clones released IL-2, IL-8, TNF-alpha, GM-CSF but only a few IFN gamma and expressed high levels of mRNA for IL-2, TGF-beta and IL-10. None of the clones was found to produce IL-3, IL-4, IL-7 and TNF-beta . The data provide evidence of the existence of T-cell precursors in u ntreated AML bone marrow differentiating to cytotoxic cells with activ ity against autologous and allogeneic AML blast cells.