Immune status assay (ISA): a noninvasive procedure for studying allograft rejection

Abstract

Background: There is a need for a simple, sensitive, noninvasive technique for monitoring graft function. We report here on a simple assay called immune status assay (ISA) that determines the status of the graft by simply examining the activation status of blood T cells. Methods: Graft-derived fibroblasts were used as a source of alloantigens and the recipient blood as a source of allograft-specific peripheral blood lymphocytes (PBL). PBL were added to wells containing donor or third-party graft-derived fibroblasts in the presence or absence of interleukin-2 (IL-2). On day 4 [ 3H]thymidine incorporation was quantified after the cells were incubated for 3 days at 37 °C, in a 5% CO 2 water-jacketed incubator. The results were analyzed using the following equation: % IL2−/ IL2+= mean [ 3H] thymidine uptake in the absence of IL -2 mean [ 3H] thymidine uptake in the presence of IL -2 X100 Results: The ISA score (%IL-2−/IL-2+) correlated strongly with the outcome of the graft, as it had a sensitivity of 82% for detecting rejections (14/17), and a specificity of 81% (30/37) for detecting non-rejections. Notably, the ISA detected immune T cell activation in the blood of graft rejecting subjects, which were not detected by currently used techniques such as mixed lymphocytes reaction. Conclusion: The ISA is a straightforward procedure that detects allograft rejection with high specificity and sensitivity.