ACTIVATION ANTIGEN EXPRESSION ON PERIPHERAL-BLOOD NEUTROPHILS FOLLOWING RAT SMALL-BOWEL TRANSPLANTATION - NKR-P1 IS A NOVEL ANTIGEN PREFERENTIALLY EXPRESSED DURING ALLOGRAFT-REJECTION

This study used flow cytometric analyses to monitor activation antigen expression (MHC class II; interleukin-2 receptor, p55IL-2R and 3.2.3/ NKR-P1 antigen) on peripheral blood neutrophils following rat small bo wel transplantation. The rat 3.2.3 antigen is a member of the NKR-P1 f amily of natural killer (NR) cell-associated molecules, which are expr essed at high levels on NK cells and lymphokine-activated killer cells , and low levels on at least one T cell subset. Peripheral blood neutr ophils in normal animals express very low or undetectable levels of NK R-P1. Detectable levels of NKR-P1 were induced as early as day 1 follo wing small bowel transplantation in all allografted animals, whereas e xpression was only rarely detected in isografted animals. In addition, NKR-P1 density was significantly higher in allografted animals and wa s maintained as rejection developed. MHC class II and p55IL-2R express ion was also induced following transplantation. The mechanisms of indu ction and functional relevance of NKR-P1 expression on neutrophils rem ain to be defined. However, the concomitant increased expression of MH C class II and p55IL-2R suggest NKR-P1 to be a neutrophil activation m arker and implicate a potential role for NKR-P1(+) neutrophils in smal l bowel allograft rejection. This hypothesis is further supported by t he loss of detectable peripheral blood neutrophils only with developin g rejection. Flow cytometric analysis of neutrophil activation antigen expression may be useful for monitoring human small bowel transplant recipients.