Intragraft mRNA expression of cytokines and growth factors in human kidney allograft biopsies by in situ RT-PCR analysis.

The aim of our study was to correlate intragraft mRNA expression of cytokines and growth factors with histopathologic features in renal allograft biopsies. Fifty-six core biopsies performed in 51 kidney transplant recipients were assessed by the Banff '97 classification. Tubular and glomerular expressions of IFN-gamma, TGF-beta1, and PDGF-B as well as IL-2, IL-6, and IL-10 mRNA were assessed using semiquantitative RT-PCR in situ. No significant differences were noted between acute cellular and vascular rejection with regard to the glomerular and tubular mRNA expression of cytokines examined. We observed a positive correlation between tubular and glomerular IL-10 and IFN-gamma mRNAs during acute rejection. In chronic rejection the mRNA expression levels of IFN-gamma and IL-2, IL-6, and IL-10 did not differ from those of acute rejection; moreover, the glomerular expression of mRNA for TGF-beta1 (P < .05) and PDGF-B (P < .1) was even lower than during acute rejection episodes. Both tubular and glomerular IL-2, TGF-beta1, and PDGF-B mRNA expression levels in biopsies with acute rejection were significantly higher than in acute tubular necrosis (ATN). Biopsy samples with borderline changes exhibited the lowest levels of cytokine gene expression and were close to the intensity of control specimens obtained from living donor kidney biopsies taken during organ harvest. Our data failed to show a dichotomy between Th1 and Th2 cytokine activation in biopsy specimens from kidney allograft recipients; both Th1- and Th2-derived cytokines were involved to similar extents in rejection processes.