M-CELLS ARE DAMAGED AND INCREASED IN NUMBER IN INFLAMED HUMAN ILEAL MUCOSA

Ileocolonoscopy and biopsies of patients with spondylarthropathy revea led gut inflammation in 62% of the cases. In order to better understan d the pathogenetic mechanisms of spondylarthropathy related gut inflam mation the follicle associated epithelium was examined. Biopsies from 9 controls and 18 patients with spondylarthropathy were studied by ele ctron microscopy. Membranous (M) cells were investigated in normal and inflamed ileum. In normal mucosa M cells were scarce whereas in infla med mucosa their number was increased (up to 24% of follicle associate d epithelial cells). They showed a thin rim of cytoplasm covering grou ps of lymphocytes. In chronic ileitis necrotic M cells, ruptures of M cell cytoplasm and lymphocytes entering the gut lumen were observed. T he bursts of M cells at the top of the lymphoid follicles lead to inte rruption of the gut epithelial lining and give luminal content access to the lymphoid tissue. This pathogenetic mechanism may cause aphthoid ulcers.