We have previously reported that mouse bone marrow (BM) cells stimulated with alloantigen produce cytotoxic effector T-cell activity and produce interferon (IFN-) α β. In this report we show evidence suggesting that interleukin 2 (IL-2) may play a role in this IFN- α β production by alloantigen-stimulated BM cells. Alloantigen-induced IFN production by bone marrow cells was completely inhibited when cultures were supplemented with antisera to IL-2. Cell-free supernatants obtained at 2 days from cultures containing CS7BL 6 BM cells and irradiated DBA 2J spleen cells were also shown to contain low levels of IL-2 activity and induced significant IFN production in fresh BM cells. Different IL-2 preparations were tested for their ability to induce IFN- α β production in mouse BM cells. Mouse BM cells cultured with recombinant human IL-2 or highly purified mouse IL-2 produced high levels of IFN- α β activity after 2-3 days of culture with significant IFN activity being detected as early as 24 hr of culture. IL-2-induced IFN- α β production was partially resistant to irradiation. In contrast, irradiated (2000 rad) bone marrow cells failed to produce any IFN when cultured with alloantigen in the absence of IL-2. T-cell-depleted BM cells or BM cells obtained from C57BL 10 nude mice produced high levels of IFN- α β following stimulation with IL-2. In addition, bone marrow cells depleted of Ia+, Qa 5+, or Asialo GM1+ cells produced IFN in response to IL-2. Thus, neither T cells nor NK cells are required for IL-2-induced IFN- α β production by BM cells. The action of IL-2 on bone marrow cells to induce IFN production was mediated by the classical IL-2 receptor, since monoclonal antibodies to the IL-2 receptor present on T cells blocked this response and since bone marrow cells depleted of IL-2 receptor-bearing cells failed to produce IFN when cultured with IL-2. These results suggest that non-T cells resident in the BM have receptors for IL-2 and can produce IFN- α β upon stimulation by IL-2. Since IFN has been shown to affect different aspects of hematopoiesis, the production of IFN by BM cells stimulated by IL-2 may be important in the control of hematopoiesis. In addition, IL-2-induced IFN production may play a role in graft-versus-host disease.
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