Similar distribution of T-cell subsets in Crohn's disease and in diverticulitis provide evidence against a primary causal role for these cells in Crohn's

Background and AimsT lymphocytes are found in abnormally large numbers in the bowel in Crohns disease. This has led to the assumption by some that these cells play a causal role in the pathogenesis of what has been labelled an autoimmune disease. An alternative explanation for their presence is that, as part of the adaptive immune system, the accumulation of these cells is not a primary phenomenon, but is a secondary adaptive immune response to faecal material in the bowel wall. To distinguish between these two processes we compared the T-cell repertoire in the bowel in Crohns with that in diverticulitis, where the primary pathology is mechanical, with a subsequent immune response to the accumulated faecal material. MethodsSix cases of Crohns disease and six patients with diverticulitis were studied. Dewaxed sections of bowel were stained with Anti-CD4, Anti-CD8, Anti-FOXP3 and Anti-CD25 to identify cytotoxic T-cells, NK-Tcells; T-helper and T-reg T-cells. ResultsNo differences were found in the distribution of the different T-cell markers in either the mucosa or in areas of inflammation in the two conditions. ConclusionThe accumulation of T-lymphocytes in the bowel in Crohns disease is likely to be a sign of an adaptive immune response to faecal material within the bowel rather than an indication of a primary causal immune attack on the bowel that produces the disease.