L-Glutamic acid at a concentration of 0.1 microM was found to induce differentiation of the cell line of HL-60 promyelocytic leukemia into granulocytes or neutrophils. The HL-60 cells have no specific glutamate-binding sites, but L-glutamic acid influences the reception of several cytokines by these cells. At a concentration of 0.1 microM, L-glutamic acid completely inhibits the high-affinity binding of 125I-labeled human recombinant interleukin-1 beta (Kd = 0.32 nM) to the HL-60 cells, but does not affect their low-affinity binding (Kd = 13.3 nM) and does not change the total number of the IL-1 beta-binding sites. Preincubation of the HL-60 cells with 0.1 microM of L-glutamic acid increases 2.5 times the number of receptors for 125I-labeled human recombinant tumor necrosis factor beta. These results suggest that L-glutamic acid plays an important role in the differentiation of the blood myeloid cells.