InVivoMAb anti-mouse CD45RB

Five-year survival rates for patients diagnosed with metastatic melanoma are less than 5%. Adoptive cell transfer (ACT) has achieved an objective response of 50% by Response Evaluation Criteria in Solid Tumors (RECIST) in this patient population. For ACT to be maximally effective, the host must first be lymphodepleted. It is hypothesized that lymphodepletion may remove regulatory elements and cytokine sinks, or increase the activation and availability of antigen presenting cells (APCs). We use an in vivo model to study the ACT of tumor-associated antigen (TAA)-specific CD4+ T cells (TRP-1 cells). We have discovered that depletion of NK1.1+ cells enhances the rejection of established melanoma tumors by adoptively transferred TRP-1 CD4+ T cells. NK1.1+ cell depletion increases the number of CD4+ T cells, the serum concentration of pro-inflammatory cytokines, autoimmune vitiligo, host survival and prevented recurrence after ACT. Because multiple cells express NK1.1, we targeted different NK1.1+ cell populations using antibodies specific for NK cells, pre-mNK cells, and innate lymphoid cells (ILCs). Our data suggests that NK1.1+B220+ pre-mNK cells (also known as interferon-producing killer dendritic cells; IKDCs) are an important inhibitor of the CD4+ T cell response to melanoma. Understanding this mechanism may help design new immunotherapies to modulate the activity of pre-mNKs in the face of an antitumor immune response and inhibit their suppression of adoptively transferred T cells.

Previous studies suggested that activation of the innate immune system impairs the induction of transplantation tolerance, but the responsible inflammatory mediators have not been identified. In this study, we examined whether IL-6 and TNF-alpha promote resistance to transplantation tolerance. Using a highly immunogenic murine skin allograft model, we found that the absence of both IL-6 and TNF-alpha in the graft recipient synergized with co-stimulatory blockade to induce tolerance. Furthermore, IL-6 and TNF-alpha acted together to promote T cell alloimmune responses both in vitro and in vivo and to impair the ability of regulatory T cells to suppress effector T cell alloimmunity. In addition, deficiency of recipient IRAK-M, a negative regulator of certain innate immune pathways, augmented cellular IL-6 and TNF-alpha responses and impaired the ability of co-stimulatory blockade to extend allograft survival. In summary, IL-6 and TNF-alpha synergistically impair the efficacy of therapies that promote allograft acceptance.

Regulatory B (Breg) cells have been shown to play a critical role in immune homeostasis and in autoimmunity models. We have recently demonstrated that combined anti-T cell immunoglobulin domain and mucin domain-1 and anti-CD45RB antibody treatment results in tolerance to full MHC-mismatched islet allografts in mice by generating Breg cells that are necessary for tolerance. Breg cells are antigen-specific and are capable of transferring tolerance to untreated, transplanted animals. Here, we demonstrate that adoptively transferred Breg cells require the presence of regulatory T (Treg) cells to establish tolerance, and that adoptive transfer of Breg cells increases the number of Treg cells. Interaction with Breg cells in vivo induces significantly more Foxp3 expression in CD4(+) CD25(-) T cells than with naive B cells. We also show that Breg cells express the TGF-beta associated latency-associated peptide and that Breg-cell mediated graft prolongation post-adoptive transfer is abrogated by neutralization of TGF-beta activity. Breg cells, like Treg cells, demonstrate preferential expression of both C-C chemokine receptor 6 and CXCR3. Collectively, these findings suggest that in this model of antibody-induced transplantation tolerance, Breg cells promote graft survival by promoting Treg-cell development, possibly via TGF-beta production.

The strongly immunogenic environment in autoimmune diseases such as lupus may pose a stringent barrier to transplantation. Despite available murine models of lupus, transplant tolerance in this setting has yet to be fully investigated in highly penetrant genetic models of disease. Such studies are of clear clinical importance because lupus is a transplant indication in which transplanted kidneys have a substantially increased risk of rejection including a role for recurrent nephritis. In the fully penetrant B6.SLE123 mouse, we determined that CD4 T follicular helper and germinal center B cells were significantly expanded compared with healthy controls. We traced this expansion to resistance of effector CD4 T and B cells in B6.SLE123 mice to regulation by either CD4 T regulatory cells (CD4Tregs) or CD8 T regulatory cells (CD8Tregs), despite demonstrating normal function by Tregs in this strain. Finally, we determined that B6.SLE123 mice resist anti-CD45RB-mediated tolerance induction to foreign islet allografts, even in the absence of islet autoimmunity. Overall, B6.SLE123 lupus-prone mice are highly resistant to transplant tolerance induction, which provides a new model of failed tolerance in autoimmunity that may elucidate barriers to clinical transplantation in lupus through further cellular and genetic dissection.