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T cell expression of TIM-3 following Ag encounter has been associated with a continuum of functional states ranging from effector memory T cells to exhaustion. We have designed an in vitro culture system to specifically address the impact of anti-TIM-3/TIM-3 engagement on human Ag-specific CD8 T cells during a normal response to Ag and found that anti-TIM-3 treatment enhances T cell function. In our in vitro T cell culture system, MART1-specific CD8 T cells were expanded from healthy donors using artificial APCs. To ensure that the T cells were the only source of TIM-3, cells were rechallenged with peptide-loaded artificial APCs in the presence of anti-TIM-3 Ab. In these conditions, anti-TIM-3 treatment promotes generation of effector T cells as shown by acquisition of an activated phenotype, increased cytokine production, enhanced proliferation, and a transcription program associated with T cell differentiation. Activation of mTORC1 has been previously demonstrated to enhance CD8 T cell effector function and differentiation. Anti-TIM-3 drives CD8 T cell differentiation through activation of the mTORC1 as evidenced by increased levels of phosphorylated S6 protein and rhebl1 transcript. Altogether these findings suggest that anti-TIM-3, together with Ag, drives differentiation in favor of effector T cells via the activation of mTOR pathway. To our knowledge, this is the first report demonstrating that TIM-3 engagement during Ag stimulation directly influences T cell differentiation through mTORC1., (Copyright © 2017 by The American Association of Immunologists, Inc.)

PD-1, TIM-3, and LAG-3 are molecules shown to have immune modulatory properties, and although initially classified as indicators of T cell hyporesponsiveness, it has become clear that they are also associated with the normal course of T cell activation. Functional studies have focused mainly on CD8(+) T cells during chronic inflammation due to interest in co-opting the cellular immune response to eliminate viral or cancerous threats; however, there remains a relative lack of data regarding the expression of these molecules on CD4(+) T cells. Here, we report that expression of the immune checkpoint (IC) molecules PD-1, LAG-3, and TIM-3 are differentially expressed on CD4(+) and CD8(+) T cells in the allogeneic response resulting from a mixed lymphocyte reaction. In these studies, PD-1 expression is higher on CD4(+) T cells compared to CD8(+) T cells. In contrast, TIM-3 is expressed at higher levels on CD8(+) T cells compared to CD4(+) T cells with an apparent reciprocity in that PD-1(+) CD4(+) T cells are frequently TIM-3(lo/-), while TIM-3-expressing CD8(+) T cells are largely PD-1(lo/-). In addition, there is a decrease in the frequency of TIM-3(+) CD4(+) cells producing IFN-γ and IL-5 compared to TIM-3(+) CD8(+) cells. Lastly, the memory T cell phenotype within each IC-expressing subset differs between CD4(+) and CD8(+) T cells. These findings highlight key differences in IC expression patterns between CD4(+) and CD8(+) T cells and may allow for more effective therapeutic targeting of these molecules in the future.

Murine dendritic cells (DC) transduced to express the Type-1 transactivator T-bet (i.e. mDC.Tbet) and delivered intratumorally as a therapy are superior to control wild-type DC in slowing the growth of established subcutaneous MCA205 sarcomas in vivo. Optimal antitumor efficacy of mDC.Tbet-based gene therapy was dependent on host natural killer (NK) cells and CD8(+) T cells, and required mDC.Tbet expression of major histocompatibility complex class I molecules, but was independent of the capacity of the injected mDC.Tbet to produce proinflammatory cytokines (interleukin-12 family members or interferon-γ) or to migrate to tumor-draining lymph nodes based on CCR7 ligand chemokine recruitment. Conditional (CD11c-DTR) or genetic (BATF3(-/-)) deficiency in host antigen-crosspresenting DC did not diminish the therapeutic action of intratumorally delivered wild-type mDC.Tbet. Interestingly, we observed that intratumoral delivery of mDC.Tbet (versus control mDC.Null) promoted the acute infiltration of NK cells and naive CD45RB(+) T cells into the tumor microenvironment (TME) in association with elevated expression of NK- and T-cell-recruiting chemokines by mDC.Tbet. When taken together, our data support a paradigm for extranodal (cross)priming of therapeutic Type-1 immunity in the TME after intratumoral delivery of mDC.Tbet-based gene therapy.