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Immune checkpoint inhibitors have substantial advanced tumor treatment, but their limited benefits and strong responses in only a subset of patients remain challenging. In this study, we explored the immunomodulatory function of contactin-4 (CNTN4). CNTN4 was highly expressed in tumor tissues, and expression impaired the antitumor function of T cells. CNTN4 bound to amyloid precursor protein (APP) on T cells, which attenuated conjugation between cancer cells and T cells, and diminished T cell receptor signaling cascades. We developed an anti-CNTN4 antibody (GENA-104A16) and an anti-APP antibody (5A7) that blocked the binding between CNTN4 and APP. Administration of either GENA-104A16 or 5A7 promoted antitumor T cell responses in a syngeneic mouse model and increased tumor-infiltrating lymphocytes in vivo. Furthermore, elevated CNTN4 levels were associated with poor prognosis and negatively correlated with various cytotoxic immune-related markers. These results suggest that CNTN4-APP is an inhibitory checkpoint in T cells and represents a promising therapeutic strategy for cancer immunotherapy. Editor's summary: Contactin-4 (CNTN4) is an adhesion molecule known to engage amyloid precursor protein (APP) in the brain, but the function of this axis in T cells and antitumor immunity is not known. Jeon et al. explored the immunomodulatory role of CNTN4-APP, finding that CNTN4 expressed on tumor cells prevents T cell activation by engaging APP on T cells. They developed an anti-CNTN4 antibody (GENA-104A16) and an anti-APP antibody (5A7) and found that blocking the CNTN4-APP interaction promoted tumor killing. Expression of APP on T cells negatively correlated with response to immune checkpoint inhibitors in patients with cancer. These findings indicate that CNTN4-APP functions as an inhibitory checkpoint in T cells. —Hannah Isles [ABSTRACT FROM AUTHOR]

Cancers eventually kill hosts even when infiltrated by cancer-specific T cells. We examined whether cancer-specific T cell receptors of CD4+ T cells (CD4TCRs) from tumor-bearing hosts can be exploited for adoptive TCR therapy. We focused on CD4TCRs targeting an autochthonous mutant neoantigen that is only presented by stroma surrounding the MHC class II–negative cancer cells. The 11 most common tetramer-sorted CD4TCRs were tested using TCR-engineered CD4+ T cells. Three TCRs were characterized by convergent recombination for which multiple T cell clonotypes differed in their nucleotide sequences but encoded identical TCR α and β chains. These preferentially selected TCRs destroyed tumors equally well and halted progression through reprogramming of the tumor stroma. TCRs represented by single T cell clonotypes were similarly effective only if they shared CDR elements with preferentially selected TCRs in both α and β chains. Selecting candidate TCRs on the basis of these characteristics can help identify TCRs that are potentially therapeutically effective. Editor's summary: Cancer immunotherapies using CD4 T cells with tumor-specific T cell receptors (CD4TCRs) have had varied efficacies. Here, Wolf et al. characterized CD4TCRs that specifically target unmanipulated tumor neoantigens toward better predicting the efficacy of CD4TCRs. They identified the 11 most frequently occurring CD4TCRs in mice bearing an autochthonous tumor line. Three TCRs showed evidence of convergent evolution, because T cell clonotypes had different nucleotide sequences but identical TCR α and β chains. T cell clonotype efficacy required shared CDR elements within preferentially selected TCRs in both α and β chains, thus providing valuable insights into predicting CD4TCR efficacy. —Christiana Fogg [ABSTRACT FROM AUTHOR]

Professional phagocytes like neutrophils and macrophages tightly control what they consume, how much they consume, and when they move after cargo uptake. We show that plasma membrane abundance is a key arbiter of these cellular behaviors. Neutrophils and macrophages lacking the G protein subunit Gβ4 exhibited profound plasma membrane expansion, accompanied by marked reduction in plasma membrane tension. These biophysical changes promoted the phagocytosis of bacteria, fungus, apoptotic corpses, and cancer cells. We also found that Gβ4-deficient neutrophils are defective in the normal inhibition of migration following cargo uptake. Sphingolipid synthesis played a central role in these phenotypes by driving plasma membrane accumulation in cells lacking Gβ4. In Gβ4 knockout mice, neutrophils not only exhibited enhanced phagocytosis of inhaled fungal conidia in the lung but also increased trafficking of engulfed pathogens to other organs. Together, these results reveal an unexpected, biophysical control mechanism central to myeloid functional decision-making. Editor's summary: Phagocytosis represents a core innate immune function of many myeloid cells, but how cell-intrinsic biophysical properties affect this process is not fully understood. Winer et al. found that deletion of the G protein subunit Gβ4 in neutrophils and macrophages increased their phagocytic capacity for a wide range of pathogen and cellular targets. The enhanced phagocytic responses in Gβ4-deficient neutrophils were accompanied by plasma membrane expansion, and both of these phenotypes required intact sphingolipid synthesis. Lung neutrophils in mice lacking Gβ4 more readily cleared the fungal pathogen Aspergillus fumigatus, leading to superior antifungal immunity. Together, these findings identify a Gβ4-dependent pathway that negatively regulates phagocytosis by controlling plasma membrane abundance in myeloid cells. —Claire Olingy [ABSTRACT FROM AUTHOR]

Understanding the mechanisms that regulate T cell immunity is critical for the development of effective therapies for diseases associated with T cell dysfunction, including autoimmune diseases, chronic infections, and cancer. Co-inhibitory "checkpoint molecules," such as programmed cell death protein-1, balance excessive or prolonged immune activation by T cell–intrinsic signaling. Here, by screening for mediators of natural killer (NK) cell recognition on T cells, we identified the immunoglobulin superfamily ligand B7H6 to be highly expressed by activated T cells, including patient-infused CD19-targeting chimeric antigen receptor (CAR) T cells. Unlike other checkpoint molecules, B7H6 mediated NKp30-dependent recognition and subsequent cytolysis of activated T cells by NK cells. B7H6+ T cells were prevalent in the tissue and blood of several diseases, and their abundance in tumor tissue positively correlated with clinical response in a cohort of patients with immune checkpoint inhibitor–treated esophageal cancer. In humanized mouse models, NK cell surveillance via B7H6 limited the persistence and antitumor activity of CAR T cells, and its genetic deletion enhanced T cell proliferation and persistence. Together, we provide evidence of B7H6 protein expression by activated T cells and suggest the B7H6-NKp30 axis as a therapeutically actionable NK cell–dependent immune checkpoint that regulates human T cell function. Editor's summary: Natural killer (NK) cells can eliminate infected or malignant cells, but they are also believed to be capable of killing host immune cells. By screening NK cell ligands on human T cells, Kilian et al. found that the immunoglobulin superfamily ligand B7H6 promotes cytolysis of activated T cells by NK cells. In leukemia-bearing humanized mice, NK cells restricted the antitumor activity of chimeric antigen receptor (CAR) T cells in a B7H6-dependent manner. A higher ratio of intratumoral NK to T cells was associated with poor response to immune checkpoint inhibition in a cohort of patients with esophageal cancer. These findings demonstrate that B7H6 recognition by NK cells can restrict human antitumor T cell responses. —Claire Olingy [ABSTRACT FROM AUTHOR]

Dendritic cells (DCs) are professional antigen-presenting cells, orchestrating innate and adaptive immunity during infections, autoimmune diseases, and malignancies. Since the discovery of DCs almost 50 years ago, our understanding of their biology in humans has increased substantially. Here, we review both antitumor and tolerogenic DC responses in cancer and discuss lineage-specific contributions by their functionally specialized subsets, including the conventional DC (cDC) subsets cDC1 and cDC2, the newly described DC3, and the plasmacytoid DCs (pDCs), focusing on the human setting. In addition, we review the lineage-unrestricted "mature DCs enriched in immunoregulatory molecules" (mregDC) state recently described across different human tumors. [ABSTRACT FROM AUTHOR]