Making antigen invisible: a coinhibitory molecule regulates the interaction between T cells and dendritic cells

Rationale for a Multimodality Strategy to Enhance the Efficacy of Dendritic Cell-Based Cancer Immunotherapy

Dendritic cells (DC), master antigen-presenting cells that orchestrate interactions between the adaptive and innate immune arms, are increasingly utilized in cancer immunotherapy. Despite remarkable progress in our understanding of DC immunobiology, as well as several encouraging clinical applications – such as DC-based sipuleucel-T for metastatic castration-resistant prostate cancer – clinically effective DC-based immunotherapy as monotherapy for a majority of tumors remains a distant goal. The complex interplay between diverse molecular and immune processes that govern resistance to DC-based vaccination compels a multimodality approach, encompassing a growing arsenal of antitumor agents which target these distinct processes and synergistically enhance DC function. These include antibody-based targeted molecular therapies, immune checkpoint inhibitors, therapies that inhibit immunosuppressive cellular elements, conventional cytotoxic modalities, and immune potentiating adjuvants. It is likely that in the emerging era of “precision” cancer therapeutics, tangible clinical benefits will only be realized with a multifaceted – and personalized – approach combining DC-based vaccination with adjunctive strategies.

Upregulation of PD-1 on CD4⁺CD25⁺ T cells is associated with immunosuppression in liver of mice infected with Echinococcus multilocularis

Alveolar echinococcosis is a zoonotic disease caused by Echinococcus multilocularis (E. multilocularis) infection. The relationship between PD-1/PD-L1 pathway and Tregs at different stages of E. multilocularis infection has rarely been reported. This study aims to investigate the role of PD-1/PD-L1 in immunosuppression of Tregs in E. multilocularis infection. Hematoxylin-eosin staining, flow cytometry, immunohistochemistry, quantitative RT-PCR analysis, cytometric bead array and MTT assay were used to analyze liver pathological changes, percentages of PD-1(+) Tregs and PD-L1(+) dendritic cells (DCs), expression levels of PD-1, PD-L1 and Foxp3, levels of interleukin-10 (IL-10) and transforming growth factor beta (TGF-β) and proliferation of lymphocytes. During middle-late stage (day 30 to day 330) the percentages of PD-1(+) Tregs and PD-L1(+) DCs together with levels of Foxp3, IL-10 and TGF-β increased significantly and maintained at high level. The expression of PD-1 and PD-L1 was increased with the enlarging erosion of E. multilocularis, and was mainly distributed in hepatic sinus, fibrous wall of alveolar hydatid and germinal layer around foci of infection. PD-1/PD-L1 promoted the secretion of IL-10 and TGF-β. Our results indicate that engagement of the PD-1 and PD-L1 correlates with inhibition of T-cell effector function, cytokine secretion and proliferation. High expression of PD-1/PD-L1 may play an important role in stimulating CD4(+)CD25(+) T cells, and maintaining peripheral tolerance and immune evasion during chronic infection of E. multilocularis.