IMMUNOHISTOCHEMICAL AND IMMUNO-ELECTRON-MICROSCOPIC DETECTION OF INTERFERON-GAMMA-INDUCING FACTOR (INTERLEUKIN-18) IN MOUSE INTESTINAL EPITHELIAL-CELLS

The novel cytokine interferon-gamma-inducing factor (''interleukin-18' ') is produced by macrophage-like cells in mice with endotoxin shock a nd induces the production of interferon-gamma by T cells in vitro. To determine the physiological role for mouse interferon-gamma-inducing f actor, we studied its tissue distribution in several organs (intestine , spleen, thymus, kidney, and liver) in healthy mice of different ages , including fetal stages. Activity of the cytokine in the organ extrac ts of adult mice was measured by enzyme-linked immunosorbent assay, an d the cellular distribution of interferon-gamma-inducing factor in org ans from fetal and adult mice was determined by immunohistochemistry. Intestinal extracts of adult mice showed the highest concentrations am ong the organs studied. Other organ extracts of adult mice showed lowe r concentrations of the cytokine. Immunohistochemical analysis reveale d that interferon-gamma-inducing factor was localized in the cytoplasm of intestinal epithelial cells from fetal and adult mice. These resul ts show for the first time that intestinal epithelial cells may be the main producers of interferon-gamma-inducing factor under normal physi ological conditions and suggest that its constitutive expression in in testinal epithelial cells may have an important role in the induction of mucosal immunity.