Hirokazu Matsushita

Although in vitro observations suggest that cross-presentation of antigens is mediated primarily by CD8alpha+ dendritic cells, in vivo analysis has been hampered by the lack of systems that selectively eliminate this cell lineage. We show that deletion of the transcription factor Batf3 ablated development of CD8alpha+ dendritic cells, allowing us to examine their role in immunity in vivo. Dendritic cells from Batf3-/- mice were defective in cross-presentation, and Batf3-/- mice lacked virus-specific CD8+ T cell responses to West Nile virus. Importantly, rejection of highly immunogenic syngeneic tumors was impaired in Batf3-/- mice. These results suggest an important role for CD8alpha+ dendritic cells and cross-presentation in responses to viruses and in tumor rejection.

Cancer immunoediting is the process whereby the immune system suppresses neoplastic growth and shapes tumor immunogenicity. We previously reported that type I interferon (IFN-α/β) plays a central role in this process and that hematopoietic cells represent critical targets of type I IFN's actions. However, the specific cells affected by IFN-α/β and the functional processes that type I IFN induces remain undefined. Herein, we show that type I IFN is required to initiate the antitumor response and that its actions are temporally distinct from IFN-γ during cancer immunoediting. Using mixed bone marrow chimeric mice, we demonstrate that type I IFN sensitivity selectively within the innate immune compartment is essential for tumor-specific T cell priming and tumor elimination. We further show that mice lacking IFNAR1 (IFN-α/β receptor 1) in dendritic cells (DCs; Itgax-Cre(+)Ifnar1(f/f) mice) cannot reject highly immunogenic tumor cells and that CD8α(+) DCs from these mice display defects in antigen cross-presentation to CD8(+) T cells. In contrast, mice depleted of NK cells or mice that lack IFNAR1 in granulocytes and macrophage populations reject these tumors normally. Thus, DCs and specifically CD8α(+) DCs are functionally relevant targets of endogenous type I IFN during lymphocyte-mediated tumor rejection.

Human γδ T cells can recognize and kill non-small cell lung cancer (NSCLC) cells using the Vγ9Vδ2 T-cell receptor and/or NKG2D. We have established clinical grade large-scale ex vivo expansion of γδ T cells from peripheral blood mononuclear cells by culturing with zoledronate and interleukin-2 (IL-2). A phase I study was conducted to evaluate safety and potential antitumor effects of re-infusing ex vivo expanded γδ T cells in patients with recurrent or advanced NSCLC. Patient's peripheral blood mononuclear cells were stimulated with zoledronate (5 μM) and IL-2 (1000 IU/mL) for 14 days. Harvested cells, mostly γδ T cells, were given intravenously every 2 weeks without additional IL-2, a total of 6 times. The cumulative number of transferred γδ T cells ranged from 2.6 to 45.1 x 10⁹ (median, 15.7×10⁹). Fifteen patients underwent adoptive immunotherapy with these γδ T cells. There were no severe adverse events related to the therapy. Immunomonitoring data showed that with increasing numbers of infusions, the number of peripheral γδ T cells gradually increased. All patients remained alive during the study period with a median survival of 589 days and median progression-free survival of 126 days. According to the Response Evaluation Criteria In Solid Tumors, there were no objective responses. Six patients had stable disease, whereas the remaining 6 evaluable patients experienced progressive disease 4 weeks after the sixth transfer. We conclude that adoptive transfer of zoledronate-expanded γδ T cells is safe and feasible in patients with NSCLC, refractory to other treatments.