Inhibition of De Novo Autoantibody Production Attenuates Chronic Antibody-Mediated Rejection of Kidney Allografts Despite Maintenance of High Donor-Specific Antibody Titers.

Acute and chronic antibody mediated rejection (ABMR) continues to decrease clinical kidney graft function and survival. Dysregulated donor-specific antibody (DSA) responses are induced in B6.CCR5(-/-) recipients of complete MHC-mismatched A/J kidney allografts with NK cells playing a critical role in the acute ABMR. We tested the role of neutrophils in ABMR by transplanting A/J kidneys to CCR5(-/-) mice with a deletion in the neutrophil serine protease cathepsin G. Whereas B6.CCR5(-/-) recipients rejected all kidney allografts between days 18-25, 70% of allografts survived beyond day 60 in B6.CCR5(-/-)cG(-/-) recipients. At days 15-17 post-transplant DSA titers in B6.CCR5(-/-)cG(-/-) recipients were 24.3-fold higher than those in wild-type C57BL/6 allograft recipients. Allografts from B6.CCR5(-/-)cG(-/-) recipients on days 45 and 60 had typical characteristics of chronic graft injury including interstitial collagen deposition and peri-glomerular fibrosis that was accompanied by a fibrogenic transcript signature and late post-transplant production of autoantibodies to many targets, including structural proteins including collagen IV and fibronectin. Depletion of B cells at the time DSA peak titers were achieved on day 14 post-transplant decreased serum autoantibodies levels, the kidney allograft fibrogenic transcript signature, and the chronic kidney allograft injury, despite maintenance of the high DSA titers. These results indicate a critical role for neutrophil cathepsin G during acute ABMR of kidney allografts and in its absence, DSA induced late appearance of autoantibodies mediating development of chronic kidney allograft injury.