Histopathology of cell mediated immune reaction in mouse colon--allograft rejection.

Grafts of mouse fetal colon, implanted beneath the renal capsule of adult hosts, have been used to study the growth and development of colonic isografts and the rejection of colonic allografts. Isografts grew normally and maintained a structure similar to normal colon. Grafts between strains with H2 histocompatibility differences were rejected by 13 days after transplantation. Early progressive infiltration of the grafts by lymphoid cells was followed by increasing damage to, and subsequent loss of, the epithelial cell layer and destruction of the underlying muscle, changes which parallel those seen in rejection of skin and small bowel. The increase in survival time which is seen in allografts between strains with H2 identity was longer in the colon than has been seen in the skin or small bowel; none of the allografts of colon were completely rejected before 30 days, and some remained viable at 50 days. Comparison of the appearances of rejection in the colon with those of ulcerative colitis and colonic Crohn's disease does not show the striking similarity which is seen between small bowel rejection and coeliac disease. Many of the individual features of these diseases are, however, present in the course of colonic rejection.