Use of stimulating capacity of mixed lymphocyte reaction (MLR-S) as a possible marker for the cell-origin of null-cell acute lymphoblastic leukaemia.

The recent introduction of surface marker analysis indicates that the T-cell ALL represents 15--25%, the B-cell ALL represents less than 5% and the null-cell ALL represents more than 70% of cases. The origin of leukaemic null-cells is at present not clear. The present study shows that fresh leukaemic cells from five patients with null-cell ALL exerted a strong stimulating effect while the leukaemic cells from three patients with null-cell ALL failed to stimulate in 'one-way' MLR. Cultured leukaemic cells from three null-cell lines (NALM-16, NALL-1 and MOLT-10) consistently exerted a strong stimulation while leukaemic cells from one null-cell line (REH) exerted little or no stimulation on allogeneic lymphocytes. Leukaemic null-cells from the NALM-,6 line exhibited a lesser but significant stimulation in 'one-way' MLR. These observations lead us to speculate that leukaemic null-cells which possess a stimulating capacity may represent less differentiated leukaemic B lymphoid cells (early B-cell precursors) and leukaemic null-cells which possess no stimulating capacity may represent less differentiated leukaemic T lymphoid cells (early T-cell precursor).