No abstract

T cell depletion is commonly used in organ transplantation for immunosuppression; however, a restoration of T cell homeostasis following depletion leads to increased memory T cells, which may promote transplant rejection. The cytokine IL-7 is important for controlling lymphopoiesis under both normal and lymphopenic conditions. Here, we investigated whether blocking IL-7 signaling with a mAb that targets IL-7 receptor α (IL-7Rα) alone or following T cell depletion confers an advantage for allograft survival in murine transplant models. We found that IL-7R blockade alone induced indefinite pancreatic islet allograft survival if anti-IL-7R treatment was started 3 weeks before graft. IL-7R blockade following anti-CD4-and anti-CD8-mediated T cell depletion markedly prolonged skin allograft survival. Furthermore, IL-7 inhibition in combination with T cell depletion synergized with either CTLA-4Ig administration or suboptimal doses of tacrolimus to induce long-term skin graft acceptance in this stringent transplant model. Together, these therapies inhibited T cell reconstitution, decreased memory T cell numbers, increased the relative frequency of Tregs, and abrogated both cellular and humoral alloimmune responses. Our data suggest that IL-7R blockade following T cell depletion has potential as a robust, immunosuppressive therapy in transplantation.

TNF blockade modulates many aspects of the immune response and is commonly used in a wide array of immune-mediated inflammatory diseases. As anti-TNF induces anti-dsDNA IgM antibodies but not other antinuclear reactivities in human arthritis, we investigated here the effect of TNF blockade on the induction of TD humoral responses using cardiac allograft and xenograft models. A single injection of an anti-rat TNF antibody in LEW.1A recipients grafted with congenic LEW.1W hearts almost completely abrogated the induction of IgM and IgG alloantibodies. This was associated with decreased Ig deposition and leukocyte infiltration in the graft at Day 5. TNF blockade did not affect germinal-center formation in the spleen or expression of Th1/Th2 cytokines, costimulatory and regulatory molecules, and TLRs in spleen and graft of the recipient animals. Clinically, the abrogation of the induction of the alloantibodies was associated with a marked prolongation of graft survival. In contrast, anti-TNF did not alter acute xenograft rejection mediated by TI antibodies in a hamster-to-rat model. Taken together, these data indicate that TNF blockade abrogates the induction of TD humoral responses and accordingly, may have a beneficial effect in antibody-mediated inflammatory pathologies.

Multiple sclerosis is an autoimmune disease of the central nervous system (CNS). Yet, the autoimmune targets are still undefined. The extracellular e1 sequence of KCNJ10, the inwardly rectifying potassium (Kir) channel 4.1, has been subject to fierce debate for its role as a candidate autoantigen in multiple sclerosis. Kir4.1 is expressed in the CNS but also in peripheral tissues, raising concerns about the CNS-specificity of such autoreactivity. Immunization of C57Bl6/J female mice with the e1 peptide (amino-acids 83-120 of Kir4.1) induced anti-e1 immunoglobulin G (IgG) and T cell responses, and promoted demyelinating encephalomyelitis with B cell CNS enrichment in leptomeninges and T cells/macrophages in CNS parenchyma from forebrain to spinal cord, mostly in the white matter. Within our cohort of multiple sclerosis patients (n = 252), six percent exhibited high anti-e1 IgG levels in serum as compared to 0.7% in the control cohort (n = 127; P = 0.015). Immunolabeling of Kir4.1-expressing white matter glia with the anti-e1 serum from immunized mice increased during murine autoimmune neuroinflammation and in multiple sclerosis white matter as compared with controls. Strikingly, the mouse and human anti-e1 sera labeled astrocytoma cells when N-glycosylation was blocked with tunicamycin. Western blot confirmed that neuroinflammation induces Kir4.1 expression, including its shorter aglycosylated form in murine experimental autoencephalomyelitis and multiple sclerosis. In addition, recognition of Kir4.1 using mouse anti-e1 serum in Western blot experiments under unreduced conditions or in cells transfected with the N-glycoslylation defective N104Q mutant as compared to the wild type further suggests that autoantibodies target an e1 conformational epitope in its aglycosylated form. These data highlight the e1 sequence of Kir4.1 as a valid CNS autoantigen with a disease/tissue-specific post-translational antigen modification as potential contributor to autoimmunity in some multiple sclerosis patients.