Mechanisms of graft versus host disease produced by small bowel transplantation

Mechanisms of graft versus host disease have been studied in Lew x BN animals transplanted with a Lew small bowel. Grafted mesenteric lymph nodes but not host mesenteric lymph nodes or host spleen, in small bowel transplanted rats undergoing lethal GVHD, provide a source of CTL with specific anti-recipient cytotoxic activity. Host MLN and host spleen display anti-recipient CTL activity only when GVHD is provoked by intraperitoneal lymphocyte injection. These data demonstrate that lethal GVHD after SBTx may occur in the absence of detectable cytotoxic activity in host lymphoid tissues, suggesting that other mechanisms are involved in the pathogenesis of GVHD after SBTx. GVHD after SBTx or lymphocyte transfer is associated with the appearance of TNF in the serum. The intensity and reversibility of this phenomenon correlate with both the clinical severity and the lethality of GVHD. Taken together these data highly suggest that TNF is directly involved in the pathogenesis of GVHD after SBTx.