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 Sjögren's 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)-gamma 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-gamma 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-gamma 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-gamma or IL-10 and that most CD4(+) T cells were positive for IL-10, although the population of IFN-gamma-positive CD4(+) T cells was low. In our experimental colitis model, Mac-1(+) macrophages that produce both IFN-gamma and IL-10 might play a crucial role in the pathogenesis of colitis in combination with CD4(+) T cells.