Prolonged cold ischemia storage of renal allografts shifts DSA specificity and enhances glomerular injury.

Abstract

Abstract Prolonged cold ischemia storage (CIS) of donor organs is a major risk factor for allograft injury. We tested how increased CIS time influences humoral alloimmunity in a mouse model of renal transplantation. B6 (H-2b) mice received BALB/c (H-2d) renal allografts subjected to 0.5 h or 6 h CIS. At 14 d posttransplant, 6 h CIS recipients had increased titers of donor-MHC class II but not class I reactive IgG DSA, elevated frequencies of both class I and class II-reactive antibody secreting cells, higher frequencies of donor-reactive IFNγ-secreting T cells and higher proportion of graft glomeruli infiltrated with macrophages compared to 0.5 h CIS controls. B cell depletion inhibited DSA generation, intragraft C4d deposition and macrophage glomerular infiltration on d14. Regardless of CIS duration, serum creatinine levels at d 60 posttransplant were comparable to non-transplanted mice. By d 60, 0.5 h CIS grafts had moderate segmental sclerosis in a limited number of glomeruli. In contrast, 6 h CIS grafts had extensive glomerular injury including thickened capillary loops, sclerosis, thrombotic microangiopathy, intracapillary fibrin thrombi, and mesangiolysis, and elevated intragraft levels of acute kidney injury markers NGAL and osteopontin. In addition, 6 h CIS recipients had increased serum levels of anti-class II but not anti-class I IgG DSA whereas the frequencies of IFNγ-producing donor-reactive T cells were low and comparable in both groups. Our findings suggest that the augmented humoral rather than cellular immune responses account for the transplant glomerulopathy after prolonged CIS. Posttransplant inflammation spreads the specificity of DSA responses from class I to class II and may thus influence renal allograft pathology.