INTRAGRAFT T-CELL RECEPTOR TRANSCRIPT EXPRESSION IN HUMAN RENAL-ALLOGRAFTS

Allograft rejection is a T cell-dependent process. It is not known whe ther rejection is mediated by a limited number of T cell clones or by a polyclonal population of T cells. Several studies attempting to answ er this question using molecular techniques to analyze the T cell rece ptor (TCR) population have reached conflicting conclusions. Reverse tr anscription-assisted polymerase chain reaction (PCR) has been used to quantify T cell infiltration and examine TCR heterogeneity in kidney t ransplant biopsies from patients experiencing graft dysfunction. RNA f rom snap-frozen biopsies gathered on 23 transplant patients was revers e transcribed to cDNA and used as the template for PCR, The constant r egion gene of the TCR beta chain (C beta), 22 different variable regio n genes of the TCR beta chain (V beta) and the constitutively expresse d glyceraldehyde phosphate dehydrogenase (GAPD) gene were amplified, T cell infiltration, as estimated by the ratio of reverse-transcribed c DNA C beta/glyceraldehyde phosphate dehydrogenase, was significantly h igher in acute cellular rejection (ACR) (2.25) than in nonrejection (N R) (0.40, P < 0.05). The number of intragraft V beta families was high er in chronic rejection and acute cellular rejection (18 and 16.4, res pectively) than in nonrejection (8.7), Five serial biopsies from two p atients progressing to immunologic graft loss showed an increase in th e number of intragraft V beta families, The finding of increased numbe rs of TCR V beta families amplified from acutely and chronically rejec ting grafts as compared with nonrejecting grafts supports the hypothes is that, at the time of clinically apparent rejection, there is a poly clonal infiltration of T cells. Analysis of reverse transcription-PCR amplification patterns of intragraft TCR C beta and V beta gene expres sion may facilitate the diagnosis in patients whose histopathologic an alyses do not clearly indicate a specific diagnosis.