Intragraft T cell receptor transcript expression in human renal allografts.

Abstract

Allograft rejection is a T cell-dependent process. It is not known whether rejection is mediated by a limited number of T cell clones or by a polyclonal population of T cells. Several studies attempting to answer this question using molecular techniques to analyze the T cell receptor (TCR) population have reached conflicting conclusions. Reverse transcription-assisted polymerase chain reaction (PCR) has been used to quantify T cell infiltration and examine TCR heterogeneity in kidney transplant biopsies from patients experiencing graft dysfunction. RNA from snap-frozen biopsies gathered on 23 transplant patients was reverse transcribed to cDNA and used as the template for PCR. The constant region gene of the TCR beta chain (C beta), 22 different variable region genes of the TCR beta chain (V beta) and the constitutively expressed glyceraldehyde phosphate dehydrogenase (GAPD) gene were amplified. T cell infiltration, as estimated by the ratio of reverse-transcribed cDNA C beta/glyceraldehyde phosphate dehydrogenase, was significantly higher in acute cellular rejection (ACR) (2.25) than in nonrejection (NR) (0.40, P < 0.05). The number of intragraft V beta families was higher in chronic rejection and acute cellular rejection (18 and 16.4, respectively) than in nonrejection (8.7). Five serial biopsies from two patients progressing to immunologic graft loss showed an increase in the number of intragraft V beta families. The finding of increased numbers of TCR V beta families amplified from acutely and chronically rejecting grafts as compared with nonrejecting graft supports the hypothesis that, at the time of clinically apparent rejection, there is a polyclonal infilitration of T cells.