Characterization of Functional Fc-Receptor Material from Human Lymphoblastoid Cell Lines

Abstract

A xenogeneic anti-human Fc-receptor serum was prepared by injecting rabbits with Fc-receptor (FcR) material isolated from the NP-40 lysate of an IgM-secreting human lymphoblastoid cell line. By indirect immunofluorescence, the immune IgG (or F(ab′)₂ fragment) from such animals reacted with a fraction of normal human peripheral blood leukocytes (PBL), corresponding closely to the proportion of FcR-bearing cells (assessed by immune complex binding), in the same cell population. The anti-FcR serum stained almost all the cells from five surface Ig-bearing lymphoblastoid cell lines, including the original cell line from which the FcR material was obtained, but not the FcR^- T cell-like lymphoma, MOLT-4, phagocytic cells, or a granulocyte-like human cell line, K562. When human PBL were incubated with anti-FcR serum, the proportion of rosettes subsequently formed with antibody-sensitized ox erythrocytes (EA) was greatly reduced. The inhibitory activity of the antiserum was removed when it was absorbed with human PBL enriched for EA rosette-forming cells (RFC), but not human PBL depleted of such cells (T cells). The antiserum reacted with a fraction of Ig-bearing lymphocytes in normal mouse spleen and PBL, and with allogeneic activated T cells (30 to 40% FcR⁺) from irradiated F₁ hybrid mice transplanted with parental T cells, but not with normal thymocytes. The determinants recognized by the anti-FcR serum are distinct from serologically detectable β₂ microglobulin, HLA, H-2 and Ia-like determinants: a) The anti-FcR serum precipitated from an NP-40 lysate of a human lymphoblastoid cell line (WT-18), material with an apparent m.w. of 46,000 daltons and that appears distinct from Ia molecules or β₂ microglobulin. b) The anti-FcR serum did not react with MOLT-4 cells nor with T cells in normal human PBL, mouse spleen, and thymus, although these cells express serologically detectable HLA or H-2 specificities. c) The anti-FcR serum, but not an anti-human Ia-like serum, reacted with normal mouse spleen cells. d) The anti-FcR serum reacted with an FcR⁺ T cell tumor, but not with an FcR^- T cell tumor, both derived from the same AKR lymphoma.