POTENTIAL ANTILEUKEMIC EFFECT OF GAMMA-DELTA T-CELLS IN ACUTE LYMPHOBLASTIC-LEUKEMIA

The immune response to leukemia is poorly understood. We postulated th at nonmalignant T lymphocytes remaining within bone marrow from childr en with newly diagnosed ALL could be involved in this immune response. T lymphocytes which expressed gamma delta TCR comprised less than 1% of ALL marrow cells. A preferential outgrowth of gamma delta T cells w ithin the CD3 population was observed when marrow cells were cultured with IL-2 alone or with stimulating feeder cells. These results, obtai ned in a series of 14 patients with precursor B-ALL, were significantl y different when compared with expansions from normal marrow cells. In one patient, the clones established from the expanded population disp layed different patterns of cytotoxicity against tumoral targets of th e B cell lineage. Some clones expressing the TCR V delta 1 segment sho wed cytotoxic activity against a cell line derived from a pre-B ALL wi thout activity against a LAK-sensitive B cell line. Using PCR amplific ation, one such clone was detected at high frequency, in the primary e xpansion of ALL marrow cells. These results suggest a prior activation in vivo of some gamma delta T cells by leukemic cells and provide som e evidence on the role of these subsets in the immune response to leuk emia.