IDENTIFICATION OF LOCALIZED ANTI-HOST RESPONSES IN THE GRAFT MESENTERIC LYMPH-NODE AND PEYERS-PATCHES AFTER RAT SMALL-BOWEL TRANSPLANTATION

This study determined the activation status of recipient and donor lym phocyte populations in the graft mesenteric lymph node (MLN) and Peyer 's patches (PP) after allogeneic, heterotopic rat small bowel transpla ntation without immunosuppression. Untransplanted and isografted anima ls served as controls. The activation status of lymphocyte subsets was determined by flow cytometric evaluation of lymphoblastoid transforma tion (forward light scatter; FSc). The proportion of activated lymphoc ytes in the MLN and PP of allografted animals progressively increased. There was also an early transient activation of MLN lymphocytes in is ografted animals which probably resulted from surgery-related inflamma tion. Activated alpha/beta TCR+ and CD4(+) cells were detected in the MLN as early as day 3, whereas there was little activation of CD8(+) c ells. Interestingly, donor lymphocytes became more activated than reci pient lymphocytes. Allografting also led to activation of graft-derive d PP alpha/beta TCR+ and CD8(+) cells, yet there was no detectable act ivation of recipient-derived lymphocytes. In summary, this study has i dentified activated donor lymphocytes in the graft MLN and PP after al logeneic small bowel transplantation. Although rejection predominates without immunosuppression, the presence of an underlying anti-recipien t response within the small bowel allograft may contribute to graft da mage via the localized release of cytokines and inflammatory mediators .