Analysis of Cytokine Production in the Colon of Nude Mice with Experimental Colitis Induced by Adoptive Transfer of Immunocompetent Cells from Mice Infected with a Murine Retrovirus

LP-BM5 murine leukemia virus (MuLV) is known to induce murine AIDS (MAIDS). We have shown that Sjögrenʹs syndrome (SjS)-like exocrinopathy can be induced in mice with MAIDS and that adoptive transfer of spleen cells from MAIDS mice can induce inflammatory bowel disease-like colitis as well as SjS-like exocrinopathy in nude mice. To assess the role of interferon (IFN)-γ and interleukin (IL)-10 in the pathogenesis of our experimental model, we tried to identify the cells producing these cytokines and their localization in the colitis lesions in situ. Expression of mRNA for IFN-γ and IL-10 was assessed by RT-PCR, and protein expression of these cytokines was also analyzed in frozen sections of colon by double-color-staining immunofluorescence (IF). An increase of IFN-γ and IL-10 mRNA was detected in the colon of mice with colitis, but not in that of control mice. Double-color IF showed that Mac-1+ cells were positive for IFN-γ or IL-10 and that most CD4+ T cells were positive for IL-10, although the population of IFN-γ-positive CD4+ T cells was low. In our experimental colitis model, Mac-1+ macrophages that produce both IFN-γ and IL-10 might play a crucial role in the pathogenesis of colitis in combination with CD4+ T cells.