NK activity during graft-versus-host disease and graft rejection in rats following intestinal semiallogenic and allogenic transplantation with or without mesenteric lymphadenectomy

Graft-versus-host disease (GVHD) and graft rejection are major problems following intestinal transplantation (IT). Natural killer (NK) cells may be important effector cells in both conditions. In this study, Sprague-Dawley (SD) or SD-Brown Norway (BN) F₁ rat intestine was transplanted into BN recipients with and without associated graft mesenteric lymphadenectomy (GML). Cyclosporine (15 mg/kg day) was administered to all animals. Pieces of the intestinal graft were examined 4 days posttransplant and again at death. NK activity calculated using intestinal intraepithelial lymphocytes (IL) was determined utilizing an 18-hr cytotoxic assay assessing ⁵¹Cr release and the results are reported as lytic units. YAC-1 cells were used as the target. NK activity was reduced 4 days after IT both in native (8.02±0.64) and in grafted bowel (3.14±1.51), with histological evidence of rejection as compared with that of control bowel in ungrafted rats (21.1 ±2.14). Survival was increased, on mean, a total of 6 days with the addition of GML in both semiallogenic and allogenic transplanted rats. At the time of death, the NK activity in the native bowel had increased (17.1 ±3.02) and histologic evidence of GVHD was present. These data suggest that: (1) NK cells are important in GVHD and (2) both semiallogenic and allogenic transplants survive longer if they are combined with GML (P≤0.05 and P≤0.01, respectively).