The interaction of mucosal lymphocytes and intestinal epithelial cells is thought to be important in regulating immune response in the intestinal mucosa, but conclusive evidence is limited. Here we demonstrate the expression of IL-7 mRNA in human intestinal mucosa by combined reverse transcription PCR and Southern blot hybridization. Immunohistochemistry and in situ hybridization confirm the presence of IL-7 in intestinal epithelial cells, especially in epithelial goblet cells. Moreover, IL-7 receptor expression in mucosal lymphocytes is demonstrated by immunohistochemistry and in situ hybridization, as well as by Southern blot and flow cytometric analysis of freshly isolated lamina propria lymphocytes. In contrast, IL-7 receptor could not be detected in the cell surface of freshly isolated PBLs. The functional activity of IL-7 receptor is demonstrated by the utility of recombinant IL-7 to stimulate the growth of lamina propria lymphocytes, and conversely inhibit CD3-dependent proliferation of these cells. In contrast, IL-7 caused no significant increase in DNA synthesis and cell numbers when added to PBLs. These findings suggest that human intestinal epithelial cells and epithelial goblet cells produce IL-7, and locally produced IL-7 may serve as a potent regulatory factor for intestinal mucosal lymphocytes.