Overall, these findings suggest that the beneficial effect of MSCs in experimental autoimmune encephalomyelitis is mainly the result of an interference with the pathogenic autoimmune response.

IntroductionTraditionally associated with the allergic response, mast cells (MCs) are now viewed as important players in a variety of immune processes, such as pathogen clearance, graft acceptance, tumor immunity, and many inflammatory and autoimmune diseases, where they exhibit either pro-or anti-inflammatory potential depending on the context. 1 Interactions of MCs with T cells have a functional role in some T cell-mediated pathologies, such as neutrophilic airway inflammation, 2,3 and autoimmune disease of the central nervous system (CNS). 4 MC-deficient mouse models show reduced development of both allergic and neutrophilic airway hyperreactivity (AHR). 2,3 MCderived tumor necrosis factor-␣ (TNF-␣) is required for T helper cell (Th17) development in the lung on ovalbumin (OVA) challenge of OTII transgenic mice, 3 a neutrophilic AHR model strictly dependent on interleukin-17 (IL-17). 5 In multiple sclerosis, MCs colocalize with demyelinating plaques in inflamed brain, and many MC-associated markers have been detected in the affected tissue. 6 The MC-deficient strain Kit W/W-v shows decreased incidence and severity of experimental autoimmune encephalomyelitis (EAE), the rodent model of multiple sclerosis. 7 MCs could be directly activated during EAE by either the specific myelin peptides or locally released agonists, including complement, cytokines, and neuropeptides, but also indirectly stimulated via Fc⑀RI by specific IgE elicited on activation of Th2 response. 1,8 In the CNS, the local release of inflammatory cytokines, proteases, oxygen radicals, and chemokines by MCs directly contributes to myelin degradation, disruption of the blood-brain barrier, and recruitment and activation of other immune cells as T lymphocytes and granulocytes in the brain parenchyma, thus exacerbating the effector phase of autoimmune response. 4 MCs are also thought to be involved in initiating EAE, through the interaction with dendritic cells and T cells in secondary lymphoid organs. 9 IL-17-secreting Th17 are considered one of the major pathogenic immune components in both EAE 10 and neutrophilic AHR. 3 Th17 cells differentiate from uncommitted precursors on antigenic activation and costimulation in the concomitant presence of a suppressive and a pro-inflammatory signal delivered by transforming growth factor-␤ (TGF-␤) and IL-6 and/or IL-21, respectively. Once primed in lymph nodes, pathogenic Th17 cells reach the inflamed tissue where they recruit granulocytes and intensify inflammation. 11 Regulatory T cells (Tregs) are one of the most relevant sources of TGF-␤ both in vitro and in vivo. This CD4 ϩ T lymphocyte subset, characterized by the constitutive expression of several costimulatory molecules and the transcription factor Foxp3, is endowed with immune-suppressive properties necessary to induce and maintain tolerance. 12 Recent findings support the notion of Treg plasticity in vivo because inflammatory stimuli can counteract Treg suppression and even promote differentiation into pathogenic Th17 cells. 13 MCs may directly or...

BackgroundThe dismal survival of glioblastoma (GBM) patients urgently calls for the development of new treatments. Chimeric antigen receptor T (CAR-T) cells are an attractive strategy, but preclinical and clinical studies in GBM have shown that heterogeneous expression of the antigens targeted so far causes tumor escape, highlighting the need for the identification of new targets. We explored if B7-H3 is a valuable target for CAR-T cells in GBM.MethodsWe compared mRNA expression of antigens in GBM using TCGA data, and validated B7-H3 expression by immunohistochemistry. We then tested the antitumor activity of B7-H3-redirected CAR-T cells against GBM cell lines and patient-derived GBM neurospheres in vitro and in xenograft murine models.FindingsB7-H3 mRNA and protein are overexpressed in GBM relative to normal brain in all GBM subtypes. Of the 46 specimens analyzed by immunohistochemistry, 76% showed high B7-H3 expression, 22% had detectable, but low B7-H3 expression and 2% were negative, as was normal brain. All 20 patient-derived neurospheres showed ubiquitous B7-H3 expression. B7-H3-redirected CAR-T cells effectively targeted GBM cell lines and neurospheres in vitro and in vivo. No significant differences were found between CD28 and 4-1BB co-stimulation, although CD28-co-stimulated CAR-T cells released more inflammatory cytokines.InterpretationWe demonstrated that B7-H3 is highly expressed in GBM specimens and neurospheres that contain putative cancer stem cells, and that B7-H3-redirected CAR-T cells can effectively control tumor growth. Therefore, B7-H3 represents a promising target in GBM.FundAlex's Lemonade Stand Foundation; Il Fondo di Gio Onlus; National Cancer Institute; Burroughs Wellcome Fund.

Mast cell (MC)-deficient c-Kit mutant Kit W/W-v mice are protected against experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis, suggesting a detrimental role for MCs in this disease. To further investigate the role of MCs in EAE, we took advantage of a recently characterized model of MC deficiency, Kit W-sh/W-sh . Surprisingly, we observed that myelin oligodendrocyte glycoprotein (MOG) 35-55 -induced chronic EAE was exacerbated in Kit W-sh/W-sh compared with Kit þ / þ mice. Kit W-sh/W-sh mice showed more inflammatory foci in the central nervous system (CNS) and increased T-cell response against myelin. To understand whether the discrepant results obtained in Kit W-sh/W-sh and in Kit W/W-v mice were because of the different immunization protocols, we induced EAE in these two strains with varying doses of MOG and adjuvants. Although Kit W-sh/W-sh mice exhibited exacerbated EAE under all immunization protocols, Kit W/W-v mice were protected from EAE only when immunized with high, but not low, doses of antigen and adjuvants. Kit W-sh/W-sh mice reconstituted systemically, but not in the CNS, with bone marrow-derived MCs still developed exacerbated EAE, indicating that protection from disease could be exerted by MCs mainly in the CNS, and/or by other cells possibly dysregulated in Kit W-sh/W-sh mice. In summary, these data suggest to reconsider MC contribution to EAE, taking into account the variables of using different experimental models and immunization protocols. MCs are key factors in IgE-associated immediate hypersensitivity reactions, during which they release a wide spectrum of inflammatory mediators in response to IgE and antigen (Ag) stimulation. 1 However, recent findings have pointed out that MCs may exert also important effector and/or immunomodulatory functions in other physiopathological conditions as venom detoxification, pathogen clearance, tumor growth, contact hypersensitivity, allograft acceptance and autoimmunity. 2 Most of these studies have assessed the in vivo role of MCs by the use of mouse models carrying spontaneous mutations in c-Kit receptor (WBB6F 1 -Kit W/W-v or C57BL/6-Kit W-sh/W-sh mice) or c-Kit ligand (WCB6F 1 -Kitl Sl /Kitl Sl-d ), which show severe deficiency of MC populations. 3,4 MCs may either enhance or suppress the inflammation associated to different types of autoimmune diseases. MC-deficient Kit W/W-v and Kitl Sl/Sl-d mice are protected from autoantibodymediated models of rheumatoid arthritis and bullous pemphigoid, inflammatory disorders affecting, respectively, the joint and the skin. Reconstitution of Kit W/W-v mice with bone marrow derived, in vitro cultured MCs (BMMCs) restores complete disease susceptibility in both conditions, thus indicating a proinflammatory role of these cells in such diseases. 5,6 Conversely, MCs seem to exert a protective function in experimental autoimmune glomerulonephritis, by limiting clinical and histological glomerular pathology and mortality. 7,8 However, recent work has shown that, unlike Kit W/W-v , Ki...

Histamine can modulate the cytokine network and influence Th1 and Th2 balance and Ab-isotype switching. Thus, pharmacological blockade or genetic deletion of specific histamine receptors has been shown to reduce the severity of experimental autoimmune encephalomyelitis (EAE), a prototypic Th1-mediated disease with similarities to human multiple sclerosis. To study the comprehensive contribution of endogenous histamine to the expression of EAE, we attempted to induce EAE in histidine decarboxylase-deficient mice, which are genetically unable to make histamine. In this study, we show that EAE is significantly more severe in HDC−/−, histamine-deficient mice, with diffuse inflammatory infiltrates, including a prevalent granulocytic component, in the brain and cerebellum. Unlike splenocytes from wild-type mice, splenocytes from HDC−/− mice do not produce histamine in response to the myelin Ag, whereas production of IFN-γ, TNF, and leptin are increased in HDC−/− splenocytes in comparison to those from wild-type mice. Endogenous histamine thus appears to regulate importantly the autoimmune response against myelin and the expression of EAE, in this model, and to limit immune damage to the CNS. Understanding which receptor(s) for histamine is/are involved in regulating autoimmunity against the CNS might help in the development of new strategies of treatment for EAE and multiple sclerosis.

Rigoni et al. report that hypomorphic Rag2R229Q mutation is associated with altered microbiota composition and defects in the gut–blood barrier and suggest that intestinal microbes may play a critical role in the distinctive immune dysregulation of Omenn syndrome.

The extrusion of DNA traps contributes to a key mechanism in which innate immune cells clear pathogens or induce sterile inflammation. Here we provide evidence that CD4+ T cells, a critical regulator of adaptive immunity, release extracellular threads of DNA on activation. These DNA extrusions convey autocrine costimulatory signals to T lymphocytes and can be detected in lymph nodes isolated during the priming phase of experimental autoimmune encephalomyelitis (EAE), a CD4+ T cell-driven mouse model of multiple sclerosis. Pharmacologic inhibition of mitochondrial reactive oxygen species (mtROS) abolishes the extrusion of DNA by CD4+ T cells, reducing cytokine production in vitro and T cell priming against myelin in vivo. Moreover, mtROS blockade during established EAE markedly ameliorates disease severity, dampening autoimmune inflammation of the central nervous system. Taken together, these experimental results elucidate a mechanism of intrinsic immune costimulation mediated by DNA threads released by activated T helper cells, and identify a potential therapeutic target for such disorders as multiple sclerosis, neuromyelitis optica, and CD4+ T cell-mediated disorders.

Chimeric antigen receptor (CAR) tonic signaling, defined as spontaneous activation and release of proinflammatory cytokines by CAR-T cells, is considered a negative attribute because it leads to impaired antitumor effects. Here, we report that CAR tonic signaling is caused by the intrinsic instability of the mAb single-chain variable fragment (scFv) to promote self-aggregation and signaling via the CD3ζ chain incorporated into the CAR construct. This phenomenon was detected in a CAR encoding either CD28 or 4-1BB costimulatory endodomains. Instability of the scFv was caused by specific amino acids within the framework regions (FWR) that can be identified by computational modeling. Substitutions of the amino acids causing instability, or humanization of the FWRs, corrected tonic signaling of the CAR, without modifying antigen specificity, and enhanced the antitumor effects of CAR-T cells. Overall, we demonstrated that tonic signaling of CAR-T cells is determined by the molecular instability of the scFv and that computational analyses of the scFv can be implemented to correct the scFv instability in CAR-T cells with either CD28 or 4-1BB costimulation.