Human Fcalpha/muR and pIgR distribute differently in intestinal tissues.

Fcalpha/muR, an Fc receptor for both IgA and IgM, is close to pIgR in gene location and has an Ig-like domain homologous to pIgR. In this study, we generated monoclonal antibodies and determined Fcalpha/muR and pIgR distributions in human intestinal tissues. Immunohistochemistry analysis showed that, unlike pIgR, which was expressed on epithelial cells of intestinal tissues, Fcalpha/muR was expressed mainly in the intestinal lamina propria and germinal centers of some lymphoid follicles. Double label immunohistochemistry analysis showed that Fcalpha/muR was expressed on intestinal macrophages and plasma cells. Fcalpha/muR was also expressed in Paneth cells. Similar expression patterns for Fcalpha/muR were observed in the small intestine, appendix, colon and rectum. These results indicate for the first time that Fcalpha/muR protein is expressed by human intestinal tissues. The different tissue distribution patterns indicate that Fcalpha/muR and pIgR have different roles in intestinal immunity.