Unique leukemic non-T/non-B lymphoid cell lines (REH and KM-3): absence of MLR-S and presence of suppressor cell activity for normal T-cell response.

The present study unequivocally demonstrates that leukemic non-T/non-B lymphod cells from three cell lines (NALL-1, NALM-6 and NALM-16) possess a strong stimulating capacity in "one-way" mixed lymphocyte reaction (MLR-S), while leukemic cells from two non-T/non-B cell lines (REH and KM-3) possess no MLR-S. It is speculated that leukemic non-T/non-B lymphoid cells with MLR-S may represent less differentiated leukemic B cells and leukemic non-T/B lymphoid cells without MLR-S may represent less differentiated leukemic T cells. The REH or KM-3 cells without MLR-S also act as suppressor cells on normal T lymphocyte response to mitogen and allogeneic cells by secreting a potent suppressor activity. The MOLT-4 leukemic T lymphoid cells with no MLR-S, on the other hand, do not act as suppressor cells on T lymphocyte response. The soluble factor(s) secreted by the REH or KM-3 cell line is non-toxic to T lymphocytes and heat-sensitive. A significant suppression of T lymphocyte response is still observed, even when the active material is only present for one hour prior to the addition of PHA or it is added several days after the beginning of cultures. The biological and physico-chemical nature of this active material has not been defined. Further studies are currently in progress for biological and physico-chemical characterization and isolation of the active material.