Aim: It has been suggested that appendicitis protects against ulcerative colitis. We hypothesize that early poor hygiene protects against ulcerative colitis (UC) and predisposes to appendicitis. Our aim was to elucidate the immunological characteristics of rectal mucosa in two populations protected against UC development: appendectomised subjects and inhabitants of developing countries.
Methods: this was an age-matched prospective case-control study. Each consecutive individual case appendectomised (group A) was compared to another control from a developing country (group B) and to a control from the general population (group C). Four biopsies from rectal mucosa were taken from all subjects, two for histological and two for histochemical study; specific antibodies were used for T lymphocytes CD3+, CD4+, CD8+ and B lymphocytes CD20+ populations.
Results: Mucosa samples of 45 non-smoker healthy subjects were studied, of which 15 were from group A, 15 from group B and 15 from group C. In appendectomised subjects, the proportion of CD8+ cells was higher than in the control group (p<0.001), but similar to that in B group. The proportion of CD3+ and CD20+ cells was significatively lower than in Ecuadorians, but similar to the control group. In Ecuadorians, the proportion of CD3+ and CD8+ cells was significatively higher than in the control group (p<0.001), and were similar to that of CD20+. There were no significant differences in the proportion of CD4+.
Conclusion: Appendectomy and deficient environmental hygiene are associated with an increase of CD8+ T lymphocytes in the rectal mucosa. Moreover, deficient environmental hygiene is associated with an increase of CD3+ and CD8+ lymphocytes. The CD8+ increase is the only common significant alteration in the mucosa of both groups protected against the development of ulcerative colitis, suggesting that the factors causing changes in lamina propria lymphocytes of both groups are different.