(A) In situ expression of IL-10 in the human colonic mucosa, visualized by immunofluorescence staining with anti–IL-10 monoclonal antibodies and confocal microscopy (see Methods). IL-10 (green) is mainly expressed by the epithelial cells of the crypts (C) and by a few mononuclear cells (arrows) in the lamina propria (LP). Nuclei appear in red. Original magnification, ×630 (left); ×1,000 (right). (B) Real-time PCR analysis of IL-10 mRNA levels, expressed relative to β-actin levels (see Methods), in preparations of isolated human intestinal epithelial cells (IEC) or of matching whole mucosa microdissected from normal colon. Horizontal lines represent mean value of 7 determinations from 4 patients. (C) Immunoblot analysis of IL-10 was performed as described in Methods from lysates of isolated human intestinal epithelial cells or of whole mucosa microdissected from normal colon. Shown is 1 representative experiment of 3. Numbers at left represent molecular size of standards in kDa. (D) IL-10 secretion, measured by ELISA, in 24-h explant cultures of human normal colonic mucosa (see Methods). Data are expressed as pg/mg wet tissue. Each point indicates individual explant culture; horizontal line represents mean value of 31 determinations from 8 independent experiments.