Aryl hydrocarbon receptor expression by macrophages and lymphocytes within infiltrates in BK polyomavirus associated nephropathy

BK virus nephropathy (BKPyVN) is a major complication after renal transplantation. Little is known about the intra renal immune response during BKPyVN. The role of macrophages remains elusive. The activation of aryl hydrocarbon receptor (AHR) - a transcription factor involved in drug metabolism - plays a key role in inflammation and viral tolerance through modulation of macrophages polarization. Since AHR has not been studied in kidney transplantation, our aim was to compare the AHR expression within renal grafts in BKPyVN with T-cell mediated rejection (TCMR) as a control. We evaluated AHR expression in kidney grafts from BKPyVN (n=8) with TCMR as control (n=6) among cases with available frozen material for AHR gene intragraft transcription measurement and stainings for AHR, CD68 and CD45. AHR transcription was higher in BKPyVN grafts versus TCMR (p=0.03). While CD68+ or CD45+ cell expression did not differ within infiltrates (median score=3 in both groups; p=1.0 and 0.69, respectively), a higher proportion of nuclear AHR expression was found in BKPyVN for CD68+ and CD45+ cells when compared with TCMR (score median 2 vs 0; p=0.007 and 1 vs 0; p=0.013, respectively). We describe for the first time a higher expression of AHR in inflammatory cell infiltrates from BKPyVN versus TCMR renal biopsies. Further studies are required to explore AHR as a potential target in the modulation of inflammatory response in BKPyVN with known modulating ligands