Abrogation of the alloreactive responses of cadaveric donor intestinal lymphocytes by intraoperative campath-1H exposure

A number of recent reports in clinical and experimental intestinal transplantation have suggested that the donor lymphocytes present in and around the gastrointestinal system are potent mediators of graft-versus-host (GvH) reactivity and that GvH responses may contribute to posttransplant morbidity. Therefore, we have tested the proliferative and cytotoxic capabilities of gut-associated lymphocytes from cadaveric donors obtained prerevascularization (pre-r) and about 6 hours postrevascularization (post-r) in recipients pretreated with Campath-1H antibody (alemtuzumab). Mixed lymphocyte reactions (MLR) were performed with lymphoid cells isolated from intestinal epithelial mucosa, lamina propria, and lymph nodes. The pre-r lymphocytes responded strongly to both the recipient and third-party alloantigenic stimulating cells. However, similar preparations from the post-r samples responded in MLR at significantly lower levels (P <. 01). This post-r decrease in responsiveness was not observed in similar lymphocyte samples obtained from donors of recipients not treated with Campath-1H. Both the pre-r and post-r samples had similar flow cytometric profiles, suggesting that there was no receptor loss in these lymphoid tissues by the short-term 6-hour exposure to Campath-1H given to the recipient. Conversely, in preliminary experiments where the donor were treated with Campath-1H, it was observed that very few lymphocytes could be obtained from intestinal tissues (n = 3). These results suggested that Campath-1H treatment of the recipient could bring about a drastic reduction in an otherwise strong GvH reactivity by the donor intestinal immune cells.