Search

Renal tubular epithelial cells ( TECs) are one of the main targets of alloreactive T cells during acute rejection. We hypothesize that TECs modulate the outcome of alloimmunity by executing immunosuppressive effects in order to dampen the local inflammation. We studied whether TECs possess immunosuppressive capacities and if indoleamine 2,3-dioxygenase ( IDO) might play a role in suppressing T cell alloreactivity. Next, we studied the role of programmed death ligand 1 ( PD- L1) and intercellular adhesion molecule-1 ( ICAM-1 with regard to TEC-related immunomodulatory effects. CD3/ CD28 and alloactivated peripheral blood mononuclear cells were co-cultured with activated TECs. We analysed CD4+ and CD8+ T cell proliferation and apoptosis in the absence or presence of IDO inhibitor 1-methyl- L-tryptophan (1- L- MT), anti- PD- L1 and anti- ICAM-1. Further, we examined whether inhibition of T cell proliferation was cell-cell contact-dependent. We found that TECs dose-dependently inhibited CD4+ and CD8+ T cell proliferation ( P < 0·05). Activated TECs showed significantly increased IDO activity and up-regulated PD- L1 and ICAM-1 expression. Suppressed CD4+ and CD8+ T cell proliferation was only partially restored or failed to restore using 1- L- MT. Activated TECs increased early and late apoptosis of proliferating CD4+ and CD8+ T cells; only CD4+ T cell apoptosis was statistically affected by 1- L- MT. Transwell experiments revealed that TEC-mediated immunosuppression is cell-cell contact-dependent. We found that anti- ICAM-1 affected only CD4+ T cell apoptosis and not T cell proliferation. Our data show that TECs suppress both CD4+ and CD8+ T cell proliferation contact dependently. Interestingly, inhibition of proliferation and enhancement of apoptosis of T cell subsets is differentially regulated by indoleamine 2,3-dioxygenase and ICAM-1, with no evidence for the involvement of PD- L1 in our system. [ABSTRACT FROM AUTHOR]

Background Serine protease inhibitor B9 (serpinB9) protects against granzyme B-mediated apoptosis and could help to reduce tubular damage under inflammatory conditions like interstitial nephritis. Previously, we found that tubular serpinB9 expression was increased during subclinical rejection. Here, we studied the regulation of serpinB9 expression in tubular epithelial cells (TECs) under inflammatory conditions. Methods SerpinB9 expression was analysed on messenger RNA (mRNA), and protein levels in primary human TECs were stimulated with various cytokines and pattern recognition receptor ligands and in kidney transplant biopsies obtained during different types of viral infection. Results Of the inflammatory stimuli tested, only the double-stranded RNA (dsRNA) analogue poly(I:C) promoted serpinB9 mRNA and protein expression. We found that TECs express the viral dsRNA receptors Toll-like receptor 3 (TLR3), melanoma differentiation-associated gene 5 (MDA5) and retinoic acid-inducible gene-I (RIG-I). dsRNA receptor ligands enhanced serpinB9 expression, which involved nuclear factor-kappaB (NF-κB) activation, did not require Type I interferon production and was a direct result of dsRNA receptor-induced gene transcription. In kidney transplants, serpinB9 transcription was increased during infection with cytomegalovirus, Epstein–Barr virus or BK virus compared to stable grafts. Immunohistochemistry showed that tubuli and lymphocytes expressed the inhibitor. Conclusion SerpinB9 expression in human TECs is induced by triggering of the viral dsRNA sensors TLR3, MDA5 and RIG-I. Viral dsRNA may increase the threshold for granzyme B-mediated apoptosis in TECs via serpinB9 upregulation and thus help to protect the kidney against cytotoxic insults during viral infection. [ABSTRACT FROM PUBLISHER]

SERPINB9 is the only known human intracellular inhibitor of granzyme B (GrB), the effector molecule in immunity against cytomegalovirus (CMV) and in renal allograft rejection. Therefore, using specific enzyme-linked immunosorbent assays, we addressed the presence of circulating SERPINB9 during primary CMV infection, subclinical rejection, acute rejection, and uncomplicated posttransplantation course. Soluble (s) SERPINB9 circulates in blood and increases on primary CMV infection. This increase was significantly higher in symptomatic than in asymptomatic patients. In contrast, sSERPINB9 levels did not change in response to subclinical or acute rejection. We demonstrated the presence of circulating sSERPINB9/sGrB complexes, which suggests that SERPINB9 has extracellular functions as well. [ABSTRACT FROM AUTHOR]