Quantitative regional variation in the expression of major histocompatibility class II antigens in enterocytes of the mouse small intestine.

The qualitative and quantitative expression of major histocompatibility class II antigens was investigated in the absorptive epithelium of the duodenum, jejunum, and ileum from mice of C3H/He (H-2k haplotype) and C57BL/6 (H-2b haplotype) strains by peroxidase-antiperoxidase labelling and image analysis. Immunohistochemical labelling revealed that the expression of class II antigens was greatest in the ileum and decreased proximally towards the duodenum. The villus epithelium of the duodenum showed a granular staining pattern in the apices of some cells. In the jejunum, an increased expression was demonstrated in the apical and basal cytoplasm of all cells covering the villus. Cells at the tip of the villus, in addition, showed staining of the lateral surfaces. Ileal enterocytes demonstrated the most intense immunostaining appearing in the cytoplasm and along baso-lateral surface membranes. Quantitative analyses confirmed that a highly significant (p less than 0.0001) difference in expression of class II antigens occurred in the three regions of the small intestine, which corroborated the qualitative findings. This regional variation of class II molecules by the absorptive epithelium may influence regional differences in antigen presenting functions and immune responsiveness to ingested antigens.