Role of the appendix in the pathogenesis of ulcerative colitis.

Although human appendix has been considered as a vestigial remnant, recent observations have focused attention on the role of the appendix in the pathogenesis of ulcerative colitis (UC). Many case-control studies suggest that previous appendectomy is rare in UC patients. This inverse relation is limited to patients who undergo appendectomy before the age of 20 years. Moreover, several investigators reported the improvement of UC after appendectomy, especially in young patients. In the appendix of UC patients, the CD4/CD8 ratio is significantly increased, and the proportion of CD4+CD69+ (early activation antigen) T cells, but not of CD4+HLA-DR+ (mature activation antigen) T cells, is also significantly increased. These findings suggest that the appendix may be a priming site in the development of UC. Further studies including analysis of CD4+ and CD8+ T cells are necessary to clarify the role of the appendix in the pathogenesis of UC.