M-cells: An interface of mucosal microenvironmental induction, a novel theory

Abstract

Problem: The morphological features of M-cells epithelium in nasopharyngeal, palatine (normal human and immunocompromised-applastic anaemia) and nasal (severe combined immunodeficiency mice, SCID-mice) tonsils were examined with regard to a new theory of mucosal immunity signal recognition and triggering. Methods: We used transmission electron and light microscopy. Results: M-cells (reticular) epithelium is organized likewise in normal and immunodeficient subjects. M-cells are equally well represented and better demonstrated in SCID-mice (due to the lack of lymphocytes in the passages of reticular epithelium). They seem to originate from the epithelial basal layer cell precursors, such as stem cells with multipotent differentiation ability. Their staged development initially shows resemblance to promelanocytes and chromaffin enteroendocrine cells with dark granulations. Conclusion: There is no reason to believe that lymphoid parenchyma underlying the mucosa is the causative and inductive factor for M-cells differentiation in tonsillar epithelium. The primarily triggered GLYCOCALYX-SIgA system (by foreign antigens) is acknowledged to be the initial step in the microenvironmental mucosal signal transduction pathway, activating M-cells and adaptive immunity. Novel theoretical generalizations on the mucosal lymphoepithelial pathways and functions are proposed. We assume that the protective role of M-cells-GLYCOCALYX-SIgA unit is analogous in significance to that of the mucus-cilia couple. Significance: Lymphoepithelial-GLYCOCALYX interaction is discussed on a broad theoretical basis as perspectives and a novel understanding of immunotherapy adjuvancy approaches, in regard to resistance, tolerance, and allergy manipulation protocols. Support: No government credits, grants and corporate support have been taken for this work.