Over the past decades, CD4⁺ T cells have been considered as a supporting actor in the fields of cancer immunotherapy. Until recently, accumulating evidence has demonstrated the critical role of CD4⁺ T cells during antitumor immunity. CD4⁺ T cells can either suppress or promote the antitumor cytotoxic CD8⁺ T cell responses, either in secondary lymphoid organs or in the tumor. In this review, we provide an overview of the multifaceted role of different CD4⁺ T cell subsets in cancer immune response and their contribution during cancer therapies. Specifically, we focus on the latest progress regarding the impact of CD4⁺ T cell modulation on immunotherapies and other cancer therapies and discuss the prospect for harnessing CD4⁺ T cells to control tumor progression and prevent recurrence in patients.

NK cells are critical for innate immunity–mediated protection. The main roles of NK cells rely on their cytotoxic functions or depend on the tuning of Th1 adaptive immunity by IFN-γ. However, the precise influence of inflammatory cytokines on NK cell and CD4 T lymphocyte interactions was never investigated. In this study, we provide evidence that IL-21, a cytokine produced during chronic inflammation or infectious diseases, promotes the differentiation of a specific subset of NK cells coexpressing CD86 and HLA-DR and lacking NKp44. More importantly, IL-21–propagated HLA-DR⁺ NK cells produce macrophage migration inhibitory factor and provide costimulatory signaling during naive CD4⁺ T cell priming inducing the differentiation of uncommitted central memory T cells. Central memory T cells expanded in the presence of HLA-DR⁺ NK cells are CXCR3⁺CCR6⁻CCR4⁻CXCR5⁻ and produce IL-2, as well as low levels of TNF-α. Costimulation of CD4⁺ T cells by HLA-DR⁺ NK cells prevents the acquisition of effector memory phenotype induced by IL-2. Moreover, we identified this population of NK HLA-DR⁺ macrophage migration inhibitory factor⁺ cells in inflammatory human appendix. Collectively, these results demonstrate a novel function for IL-21 in tuning NK and CD4⁺ T cell interactions promoting a specific expansion of central memory lymphocytes.

Telomerase is a prototype-shared tumor Ag and represents an attractive target for anticancer immunotherapy. We have previously described promiscuous and immunogenic HLA-DR–restricted peptides derived from human telomerase reverse transcriptase (hTERT) and referred as universal cancer peptide (UCP). In nonsmall cell lung cancer, the presence of spontaneous UCP-specific CD4 T cell responses increases the survival of chemotherapy-responding patients. However, the precise mechanisms of hTERT’s uptake, processing, and presentation on MHC-II molecules to stimulate CD4 T cells are poorly understood. In this work, by using well-characterized UCP-specific CD4 T cell clones, we showed that hTERT processing and presentation on MHC-II involve both classical endolysosomal and nonclassical cytosolic pathways. Furthermore, to our knowledge, we demonstrated for the first time that hTERT’s internalization by dendritic cells requires its interaction with surface heparan sulfate proteoglycans. Altogether, our findings provide a novel mechanism of tumor-specific CD4 T cell activation and will be useful for the development of novel cancer immunotherapies that harness CD4 T cells.

The understanding of cell-cell and cell-matrix interactions via receptor and ligand binding relies on our ability to study the very first events of their contact. Of particular interest is the interaction between a T cell receptor and its cognate peptide-major histocompatibility complex. Indeed analyzing their binding kinetics and cellular avidity in large-scale low-cost and fast cell sorting would largely facilitate the access to cell-based cancer immunotherapies. We thus propose a microfluidic tool able to independently control two types of micro-sized objects, put them in contact for a defined time and probe their adhesion state. The device consists in hydrodynamic traps holding the first type of cells from below against the fluid flow, and a dielectrophoretic system to force the second type of object to remain in contact to the first one. First the device is validated by performing an adhesion frequency assay between fibroblasts and fibronectin coated bead. Then, a study is conducted on the modification of the cellular environment to match the dielectrophoretic technology requirements without modifying the cells viability and interaction functionalities. Finally, we demonstrate the capability of the developed device to put cancer cells and a population of T cells in contact and show the discrimination between specific and non specific interactions based on pairs lifetime.

Reverse immunology has open the door to innovative cancer immunotherapy strategies such as immunogenic antigen-based vaccination and transgenic T cell receptor (TCR)-based adoptive cell transfer. This approach enables the identification of immunogenic tumor specific antigen derived peptides. One of the major challenges is the rapid selection of antigen-specific CD8+ T cell clones. Thus, IFNγ-producing CD8+ T cells magnetic sorting combined with limiting dilution cloning approach represents the most common method of specific T cell cloning. However, during plate setup several wells will not contain T cells whereas others will contain mixed population of T cells. In this case, a re-cloning step is required which make limiting dilution based cloning a laborious, inefficient, expensive and a time-consuming method. To address these obstacles, here we present a novel 2-step workflow combining simple, affordable and gentle magnetic cell separation followed by single cell isolation using a device called DispenCell-S1. We aimed to compare this new workflow with the traditional limiting dilution method using in vitro generated antigen-specific CD8+ T cells. Herein, we reported the reliability of DispenCell-S1 method and its efficiency in T cell clones isolation.