HUMAN INTESTINAL M-CELLS EXHIBIT ENTEROCYTE-LIKE INTERMEDIATE FILAMENTS

Background-The derivation and ultrastructural composition of M cells c overing the lymphoid follicles of Peyer's patches is still unknown. Re sults from different animal models have shown that there are species s pecific differences in the composition of intermediate filaments betwe en M cells and neighbouring enterocytes. Little is known, however, abo ut intermediate filaments of human M cells. Aims-To compare components of the cytoskeleton of human M cells with those of adjacent absorptiv e enterocytes. Methods-The expression and localisation of different cy tokeratins, vimentin, and desmin in M cells was determined on follicle associated epithelia of human appendix using immunohistochemistry and immunogold electron microscopy. Results-Cytokeratins specific for hum an intestinal epithelial cells such as cytokeratins 8, 18, 19, and 20 were expressed in both absorptive enterocytes and M cells with no diff erences in intensity and cellular distribution between both cell types . Vimentin and desmin, tissue specific markers of either mesenchymal o r myogenic cells, as well as other cytokeratins were not detectable in enterocytes or M cells. Conclusion-This is the first study on the str ucture of intermediate filaments in human intestinal M cells, Our resu lts show that in contrast to several animal models, human M cells appa rently do not differ from adjacent enterocytes in the composition of t heir intermediate filament cytoskeleton. The presence of enterocyte li ke cytokeratins and the absence of other cytokeratins as well as of vi mentin and desmin supports the hypothesis of an epithelial origin of h uman intestinal M cells and suggests that M cells may derive from diff erentiated enterocytes.