Chronic murine colitis is dependent on the CD154/CD40 pathway and can be attenuated by anti-CD154 administration

Background & Aims: Experimental colitis in most animal models is caused by dysregulation of T lymphocytes that display a T helper 1 (Th1) phenotype, CD154 (CD40L/gp39), a member of the tumor necrosis factor (TNF) family, is up-regulated on T cells on activation and has been shown to play a key role in the induction of a Th1 response. We investigated whether chronic experimental colitis is dependent on the CD154/CD40 pathway and whether disease can be prevented by anti-CD154 antibody treatment, Methods: Two models of chronic colitis were used: CD45Rb(hi) cell transfer into recombination activation gene-deficient (Rag(-/-)) mice and bone marrow transplant of tg epsilon 26 animals, In both models, mice were reconstituted with cells from CD154-deficient animals. In another series of experiments, wildtype CD45Rb(hi) T cell-reconstituted recipients were treated with anti-CD154, either from the start of the experiment or after onset of disease, Results: T cells deficient in CD154 induced a milder clinical disease, less weight loss, and fewer histologic signs of colitis than wild-type cells. The level of interleukin 12 in the serum of CD154-deficient T-cell recipients was 5-fold less than that of wild-type cell recipients. Nevertheless, no signs of deviation from a Th1 phenotype were observed, Treatment with anti-CD154 antibodies substantially impaired disease development, even when started after the onset of colitis, Conclusions: The CD154/CD40 pathway plays a critical role in Th1-induced chronic experimental colitis, Blocking CD154, even after the onset of disease, ameliorates colitis but does not induce a T helper 2 (Th2) phenotype.