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Head and neck cancer (HNC) is the sixth most common cancer worldwide with a five-year survival of 50%. Immunotherapy is emerging as a promising treatment modality in HNC. Pembrolizumab, an anti-PD-1 antibody, is an immunotherapy currently approved in metastatic HNC and in clinical trials for curative intent. Although there are promising responses to Pembrolizumab, its effect on cytotoxic CD8+ T cell function is not understood. T cell cytotoxicity is critically important in the elimination of tumors and in the tumor microenvironment, cytotoxicity depends on ion channel activity which is defective in HNC patients. Therefore, to elucidate mechanisms of Pembrolizumab, we studied potassium channel (KCa3.1 and Kv1.3) functionality and Ca2+ fluxes in CD8+ peripheral blood T cells (PBTs) of naïve HNC patients before/after Pembrolizumab treatment (n=22) as well as tumor infiltrating lymphocytes (TILs) functionality. Untreated HNC patients were controls (n= 13). Pembrolizumab-treated patients were categorized as responders (R) or non-responders (NR) based on pathological response. We then performed electrophysiological and Ca2+ flux experiments. We observed that Pembrolizumab increased KCa3.1 currents in PBTs (29.8%, p=0.026). Moreover, after treatment, R PBTs also had increases in Kv1.3 currents and Ca2+ fluxes (22.1%, p=0.047; 16.5%, p

Immunotherapy offers promising results in head and neck cancer (HNC) albeit it faces the problem of high resistance. PD1 (programmed death receptor-1) and its ligand (PD-L1/PD-L2) interaction reduces T cell receptor (TCR)-stimulated Ca2+ fluxes. Ion channels regulate Ca2+ entry in T cells downstream to the TCR (store-operated Ca2+ entry, SOCE). We hypothesized that anti-PD1 antibody (Pembrolizumab, Pembro) increases SOCE. We studied the effect of Pembro and PD-L1 on SOCE in CD8+ peripheral blood T cells (PBTs) of HNC patients and healthy donors (HD) using Thapsigargin (TG). Additionally, we tested the effect of Pembro on KCa3.1, Kv1.3 and Ca2+ release activated Ca2+ (CRAC) channels in PBTs of HNC patients using patch-clamp electrophysiology. TCR-mediated Ca2+ fluxes were assessed in PD1-expressing NFAT-reporter Jurkat cells. In these cells, Pembro increased the number of cells that responded to TCR stimulation with a sustained increase in Ca2+ (30%, p

The Grb2-associated binding protein 3 (Gab3) is a scaffolding protein that belongs to the Grb2-assocated binding family of proteins along with Gab1 and Gab2. Gab3 is expressed exclusively in immune cells including NK cells, CD8+T cells, mast cells and macrophages, however the function of Gab3 has remained elusive. Based on two independent mouse models; a hypomorph germline mouse model carrying a missense mutation in the PH domain of Gab3 and complete Gab3-KO mice, we uncovered a key role for Gab3 in peripheral NK cell function. Specifically, loss of Gab3 results in impaired IL-2/IL-15-induced NK cell priming and expansion, due to a selective impairment in MAPK- but not STAT5-signaling. In vivo, we show that Gab3 is required for recognition and elimination of “missing-self” and tumor targets. Gab3-deficient mice exhibit impaired uterine NK cell expansion that is associated with abnormal spiral artery remodeling and increased trophoblast invasion in the decidua basalis. This coincides with stillbirth, retained placenta, maternal hemorrhage and undelivered fetoplacental units at term. Thus, our studies identify Gab3 as a novel component required for IL-2/IL-15-mediated NK cell priming and expansion that is essential for anti-tumor responses and for controlling fetal trophoblast invasion during pregnancy.

Impaired functionality of dendritic cells (DCs) significantly contributes to decreased adaptive immune responses in aged hosts. The expression of MHC-peptide on the DC surface is the critical first step in T cell priming, but few studies have addressed the effect of aging on antigen (Ag) acquisition, processing, and presentation by DCs. Here we show that aged murine DCs were less efficient in the cross-presentation of cell-associated Ag and subsequently in the cross-priming of CD8+ T cells than their young counterparts. The decreased cross-presentation was associated with a reduction in the frequency of CD8αDCs and merocytic (CD8α-CD11b-)DCs that could endocytose cell-associated Ag, as well as the number and the size of the endocytosed particles in the DC that did internalize cell-associated materials. Mechanistically, phagocytic capacity has been associated with mitochondrial activity and membrane potential (Δψm). Aged DCs exhibited profound signs of mitochondrial dysfunction, illustrated by lower Δψm, reduced ATP turnover and coupling efficiency, decreased baseline oxidative phosphorylation (OXPHOS), and greater proton leak and ROS production. Mimicking the aged metabolic phenotype in young DCs by pharmacologic manipulation indicated that the reductions in Δψm and ATP impeded the phagocytic capacity while ROS interfered with a later step in the cross-presentation process. Conversely, in vitro scavenging of ROS partially restored cross-presentation by aged DCs. Together, these data suggest that improvement of aged DC functionality might be feasible in the elderly, by targeting metabolic dysfunction, or its downstream sequelae, thereby opening new avenues for enhancing vaccine efficiency in this population.

Pinkie is a recessive ENU-induced mutation, homozygotes develop premature graying and subsequently, progressive alopecia. Histologically, the skin is characterized by the destruction of hair follicle architecture, formation of dermal cysts and appearance of black papules throughout the ventral skin late in life. The Pinkie mutation was mapped to the retinoid X receptor alpha (Rxra) locus (chromosome 2) on 700 meioses and positionally cloned. As a component of the nuclear receptors for retinoic acid and other bioactive molecular ligands, RXRa plays an irreplaceable role during embryogenesis and a null allele of RXRa invariably causes embryonic lethality. Pinkie, which results from the amino acid substitution N273I in the ligand-binding domain, is the first viable germline hypomorphic mutation of RXRa. Transfection studies suggest that the abnormal protein retains only 10 to 20% of the activity of the wild type receptor. Pinkie homozygotes develop a progressive phenotype, part of which entails a severe, age-dependent imbalance of Th1/Th2 differentiation upon antigenic challenge. When immunized with ovalbumin (OVA), pinkie homozygotes displayed markedly decreased IgG1 levels in serum as compared with normal C57BL/6 mice; in vitro OVA re-stimulation of pinkie splenocytes causes greatly enhanced IFN-g production and decreased IL-4 production. Upon MCMV infection, pinkie homozygotes showed significantly higher type I interferon levels in serum than normal C57BL/6 mice. The in vitro differentiation of naïve CD4 T cells demonstrated skewed Th1 development in pinkie mouse compared to that of C57BL/6 control animal. However, real-time PCR didn’t reveal significant difference in mRNA level of GATA-3 and T-bet, which are believed to be critical transcription factors in Th1/Th2 development. These data collectively imply that RXRa is required for Th2 development. This requirement might reflect an influence of RXRa on the expression of pertinent transcription factors (e.g., GATA-3, T-bet), cytokines (IL-4, IFN-gamma) and/or cytokine receptors that are involved in Th1/Th2 differentiation. RXRa represents a likely interface between the nutritional environment and the immune status of the host. Consumption of retinoids and vitamin D may therefore be expected to influence the development of the allergic/atopic (Th2) phenotype, and provide a plausible explanation for the increasing frequency of atopic disease observed in developed countries.