Human intestinal M cells exhibit enterocyte-like intermediatefilaments

Background—The derivation and ultrastructuralcomposition of M cells covering the lymphoid follicles of Peyer'spatches is still unknown. Results from different animal models haveshown that there are species specific differences in the composition ofintermediate filaments between M cells and neighbouring enterocytes. Little is known, however, about intermediate filaments of human M cells.
Aims—To compare components of the cytoskeleton ofhuman M cells with those of adjacent absorptive enterocytes.
Methods—The expression and localisation ofdifferent cytokeratins, vimentin, and desmin in M cells was determinedon follicle associated epithelia of human appendix usingimmunohistochemistry and immunogold electron microscopy.
Results—Cytokeratins specific for humanintestinal epithelial cells such as cytokeratins 8, 18, 19, and 20 wereexpressed in both absorptive enterocytes and M cells with nodifferences in intensity and cellular distribution between both celltypes. Vimentin and desmin, tissue specific markers of eithermesenchymal or myogenic cells, as well as other cytokeratins were notdetectable in enterocytes or M cells.
Conclusion—This is the first study on thestructure of intermediate filaments in human intestinal M cells. Ourresults show that in contrast to several animal models, human M cellsapparently do not differ from adjacent enterocytes in the compositionof their intermediate filament cytoskeleton. The presence of enterocyte like cytokeratins and the absence of other cytokeratins as well as ofvimentin and desmin supports the hypothesis of an epithelial origin ofhuman intestinal M cells and suggests that M cells may derive fromdifferentiated enterocytes.

Keywords:human intestinal M cells; appendix; cytokeratin; intermediate filaments; follicle associated epithelium