Granulysin expression is a marker for acute rejection and steroid resistance in human renal transplantation

Differentiating etiologies of transplant dysfunction without biopsy and opt imizing therapy for acute rejection by predicting steroid resistance will r educe patient morbidity. Granulysin is a cytolytic molecule released by CTL and NK cells and coexpressed with effectors of acute allograft rejection, like perforin and granzymes. Granulysin mRNA and protein expression were st udied in peripheral blood lymphocytes (PBL; n = 61 total, n = 10 with inter current infections) and biopsy tissue from adult and children renal transpl ant recipients (n = 97) by competitive quantitative-reverse transcriptase-P CR (QC-RT-PCR) and immunohistochemistry. Differences in cell phenotypes wer e studied in steroid sensitive and resistant acute rejection biopsies. Gran ulysin was studied in phytohemagglutinin (PHA) stimulated cell lines (donor PBL and CD45RO(+) T cells) by FACS, Western blotting, and RT-PCR after pre treating with cyclosporine A (CSA), azathioprine, mycophenolic acid, and st eroids. Granulysin mRNA was significantly increased in patient PBL and tran splant biopsies during acute rejection (p < 0.0001) and infection (p < 0.00 1). Rejecting biopsies alone (n = 53) had mononuclear cell granulysin stain ing. Steroid resistant biopsies (n = 25) had denser granulysin staining (>2 cells/high power field) and CD45RO(+) lymphocytes, when compared with ster oid sensitive (n = 28) rejecting tissue. Granulysin levels were unchanged a fter azathioprine and mycophenolic acid treatment, decreased after treating activated PBL with steroids and cyclosporine A (CSA), and paradoxically, i ncreased (p < 0.05) after treating CD45RO(+) CTL with CSA. Elevated PBL gra nulysin is a peripheral marker for acute rejection and infection and dense granulysin staining a tissue marker for steroid resistance. Memory CTL abou nd in steroid resistant grafts and may have a markedly different response t o CSA immunotherapy, suggesting a possible mechanism for steroid resistance . Human Immunology 62, 21-31 (2001) (C) American Society for Histocompatibi lity and Immunogenetics, 2001. Published by Elsevier Science Inc.