Anti-huCD20 antibody therapy for antibody-mediated rejection of renal allografts in a mouse model.

We have reported that B6.CCR5(-/-) mice reject renal allografts with high serum donor-specific antibody (DSA) titers and marked C4d deposition in grafts, features consistent with antibody-mediated rejection (AMR). B6.huCD20/CCR5(-/-) mice, where human CD20 expression is restricted to B cells, rejected A/J renal allografts by day 26 posttransplant with DSA first detected in serum on day 5 posttransplant and increased thereafter. Recipient treatment with anti-huCD20 mAb prior to the transplant and weekly up to 7 weeks posttransplant promoted long-term allograft survival (>100 days) with low DSA titers. To investigate the effect of B cell depletion at the time serum DSA was first detected, recipients were treated with anti-huCD20 mAb on days 5, 8, and 12 posttransplant. This regimen significantly reduced DSA titers and graft inflammation on day 15 posttransplant and prolonged allograft survival >60 days. However, DSA returned to the titers observed in control treated recipients by day 30 posttransplant and histological analyses on day 60 posttransplant indicated severe interstitial fibrosis. These results indicate that anti-huCD20 mAb had the greatest effect as a prophylactic treatment and that the distinct kinetics of DSA responses accounts for acute renal allograft failure versus the development of fibrosis.

Acute and chronic rejection: compartmentalization and kinetics of counterbalancing signals in cardiac transplants.

Acute and chronic rejection impact distinct compartments of cardiac allografts. Intramyocardial mononuclear cell infiltrates define acute rejection, whereas chronic rejection affects large arteries. Hearts transplanted from male to female C57BL/6 mice undergo acute rejection with interstitial infiltrates at 2 weeks that resolve by 6 weeks when large arteries develop arteriopathy. These processes are dependent on T cells because no infiltrates developed in T cell-deficient mice and transfer of CD4 T cells restored T cell as well as macrophage infiltrates and ultimately neointima formation. Markers of inflammatory macrophages were up-regulated in the interstitium acutely and decreased as markers of wound healing macrophages increased chronically. Programmed cell death protein, a negative costimulator, and its ligand PDL1 were up-regulated in the interstitium during resolution of acute rejection. Blocking PDL1:PD1 interactions in the acute phase increased interstitial T cell infiltrates. Toll-like receptor (TLR) 4 and its endogenous ligand hyaluronan were increased in arteries with neointimal expansion. Injection of hyaluronan fragments increased intragraft production of chemokines. Our data indicate that negative costimulatory pathways are critical for the resolution of acute interstitial infiltrates. In the arterial compartment recognition of endogenous ligands including hyaluronan by the innate TLRs may support the progression of arteriopathy.

An IL-27/Lag3 axis enhances Foxp3+ regulatory T cell-suppressive function and therapeutic efficacy.

Foxp3-expressing regulatory T cells (Tregs) are central regulators of immune homeostasis and tolerance. As it has been suggested that proper Treg function is compromised under inflammatory conditions, seeking for a pathway that enhances or stabilizes Treg function is a subject of considerable interest. We report that interleukin (IL)-27, an IL-12 family cytokine known to have both pro- and anti-inflammatory roles in T cells, plays a pivotal role in enhancing Treg function to control T cell-induced colitis, a model for inflammatory bowel disease (IBD) in humans. Unlike wild-type (WT) Tregs capable of inhibiting colitogenic T-cell expansion and inflammatory cytokine expression, IL-27R-deficient Tregs were unable to downregulate inflammatory T-cell responses. Tregs stimulated with IL-27 expressed substantially improved suppressive function in vitro and in vivo. IL-27 stimulation of Tregs induced expression of Lag3, a surface molecule implicated in negatively regulating immune responses. Lag3 expression in Tregs was critical to mediate Treg function in suppressing colitogenic responses. Human Tregs also displayed enhanced suppressive function and Lag3 expression following IL-27 stimulation. Collectively, these results highlight a novel function for the IL-27/Lag3 axis in modulating Treg regulation of inflammatory responses in the intestine.