Immune complex-induced enteropathy. Effects of repeated injections of immune complexes on the small intestine of the rat.

Rats injected intravenously with immune complexes (IC) prepared in 5x antigen excess were reported previously to develop a distinctive striped pattern of serosal hyperemia of the small intestine accompanied by mucosal edema and hemorrhage. This study tested the effect of repeated injections of IC given at 3-day intervals. After the last of four, six, or nine injections, rats continued to show the same gross and histologic lesions observed in rats injected once with IC. After serial injections, however, the distal small intestine was more severely involved than the proximal intestine. In addition, villous shortening, stromal hemosiderin deposits, and gut-associated lymphoid tissue and mesenteric lymph node sinus hemorrhage and hemosiderin deposits were seen in rats given nine injections. There was a remarkable absence of stromal infiltration of the villi by inflammatory cells. Experiments conducted with 125I-labeled IC plus sufficient "cold" IC to induce intestinal lesions showed that IC were deposited at extravascular sites in the gut. The failure of such IC to provoke cellular infiltration in the gut is unexplained.