Natural killer (NK) cell-derived hematopoietic colony-inhibiting activity and NK cytotoxic factor. Relationship with tumor necrosis factor and synergism with immune interferon.

Abstract

We characterize the natural killer (NK) cell colony-inhibiting activity (CIA) produced in supernatants from cultures of human peripheral blood lymphocytes (PBL) with NK-sensitive target cell lines, and study its relationship with NK cell-derived cytotoxic factor (NKCF). Using monoclonal antibodies (mAb) specific for NK cells or other lymphocyte populations, we unambiguously identify NK cells as the only PBL subset able to produce both NKCF and NK-CIA. We present functional and biochemical data suggesting that NKCF and NK-CIA represent the same molecule: (a) a highly significant positive correlation exists between the quantity of NKCF and NK-CIA in supernatants independently produced by different PBL subsets; (b) both NK-CIA and NKCF are induced by culture of PBL with NK-sensitive, but not with NK-insensitive cell lines, and with HLA-DR+ bone marrow cells; (c) both NKCF and NK-CIA are absorbed on the same cell lines or bone marrow cell types; (d) the two activities coelute in the same gel filtration fractions; (e) D-mannose-6-phosphate blocks both NKCF and NK-CIA activity, and prevents their absorption by K562 cells; and (f) both NLKCF and NK-CIA activity are lost after 2 d at 37.degree. C. The NK-CIA-containing preparations are devoid of antiviral activity, and antiinterferon (anti-IFN) antibodies do not block the inhibitory activity of NK-CIA. The effect of NK-CIA on day 14 (early) colony-forming units of granulocytes and macrophages (CFU-GM) is synergistic with that of IFN-.gamma., and this synergy is also evident on day 7 (late) CFU-GM growth. A combination of NK-CIA and IFN-.gamma. suppresses late CFU-GM, at concentrations of the two lymphokines that are completely ineffective when used independently. No synergy between NK-CIA and IFN-.alpha. or -.beta. was observed, due to a direct inhibitory effect of these two IFN types on late CFU-GM. Antibodies specific for tumor necrosis factor (TNF), but not those specific for lymphotoxins, inhibit both NK-CIA and NKCF activity in the NK cell-derived supernatant. Recombinant TNF, in the range of concentrations corresponding to that of the cytotoxic activity on L-929 cells present in supernatants, mediated both NKCF and NK-CIA activity. Together, our data suggest that the molecules responsible for both the cytotoxic effect of NK cell supernatants on NK-sensitive cell lines and the cytotoxic or cytostatic effect of the same supernatants on bone marrow cells are identical, and that these molecules are antigenically, functionally, and biochemically similar to or identical with the TNF produced by human monocytes and myeloid cell lines.