Collagenous colitis: an electron microscopic study including comparison with the chronic fibrotic stage of ulcerative colitis

Abstract

Light and electron microscopic studies of 14 cases of collagenous colitis are reported. Comparative electron microscopic examinations were carried out on 13 cases of ulcerative colitis in the chronic fibrotic stage of the disease. Separation of pericryptal fibroblasts which showed enhanced fibre-forming activity, proliferation of myofibroblasts, accumulation of mast cells and a pericapillary collagen accumulation were noted in both groups. Based on these results, collagenous colitis was considered to result from scar formation secondary to previous superficial inflammation.

Microscopic Colitis

“…Although neutrophils do not dominate the inflammatory infiltrates, they are seen in patients microscopic colitis, with active cryptitis found in 30% to 40% of patients. 82 Some studies have noted mast cells in the inflammatory infiltrate 52,86,87 or embedded within the collagen layer, 88 but other studies showed no difference in the numbers compared with those in control subjects. 89 The inflammatory changes are often accompanied by surface epithelial damage or even detachment 13,41 (Fig.…”

“…2), often with entrapped blood cells and a ragged inferior edge, ranging from 7 to 80 μm, compared with 5 to 7 μm normally. 11,22,41,87 The basement membrane is normal, 88,89 although the collagen band is closely associated with it. 87,89…”

“…87,100,156 In patients with collagenous colitis, the sheath is separated from the epithelium, and the fibroblasts demonstrate increased synthetic activity, 87,156 assuming the characteristics of myofibroblasts, the proliferating cells seen in granulation tissue. 89,156 An increase in myofibroblast number and complexity, 87,157 sometimes “entrapped” within the collagen layer 12,89,100 also has been reported. It is possible that these abnormal fibroblasts produce excessive collagen, which is deposited under the basement membrane producing the subepithelial collagen band.…”

“…This conclusion is supported by the fact that changes in the pericryptal fibroblast structure and function identical to that seen in patients with collagenous were colitis also found in the chronic “fibrotic stage” of ulcerative colitis. 87…”

Foxp3 Expression Patterns in Microscopic Colitides

“…Evidence shows, however, that "autoimmune phenomena" and an abnormal immune response to luminal antigens are involved. 11 In experimental models CD4+/CD25+ regulatory T cells (Tregs) play a critical role in the maintenance of self-tolerance, control of autoimmune diseases, and transplant rejection and have been suggested as a therapeutic option in severe inflammatory colitis. [12][13][14] It has been known for more than 5 years that CD8+ T lymphocytes (CTLs) secrete interleukin (IL) 2, which stimulates Upon completion of this activity you will be able to: • define the 2 major types of microscopic colitis, their clinical symptoms, and their microscopic characteristics.…”