Low dose endoluminal photodynamic therapy improves murine T cell-mediated colitis.

BACKGROUND AND STUDY AIMS: Low dose photodynamic therapy (LDPDT) may modify the mucosal immune response and may thus provide a therapy for Crohn's disease. We evaluated the efficacy and safety of this technique in a murine T cell-mediated colitis model. METHODS: The safety of LDPDT was first tested in BALB/c mice. Naïve T cells were used to induce colitis in mice with severe combined immunodeficiency, which were followed up endoscopically, and a murine endoscopic index of colitis (MEIC) was developed. The efficacy of LDPDT (10 J/cm (2); delta-aminolevulinic acid, 15 mg/kg bodyweight) was then tested on mice with moderate colitis, while a disease control group received no treatment. The MEIC, weight, length, and histology of the colon, cytokine expression indices, number of mucosal CD4 (+) T cells, percentage of apoptotic CD4 (+) T cells, body weight, and systemic side effects were evaluated. RESULTS: LDPDT improved the MEIC ( P = 0.011) and the histological score ( P = 0.025), diminished the expression indices of the proinflammatory cytokines, interleukin-6 ( P = 0.042), interleukin-17 ( P = 0.029), and interferon-gamma ( P = 0.014), decreased the number of mucosal CD4 (+) T cells, and increased the percentage of apoptotic CD4 (+) T cells compared with the disease control group. No local or systemic side effects occurred. CONCLUSION: LDPDT improves murine T cell-mediated colitis, decreases the proinflammatory cytokines interleukin-6, interleukin-17, and interferon-gamma, and decreases the number of CD4 (+) T cells. No adverse events were observed. Therefore, this technique is now being evaluated in patients with inflammatory bowel disease.

Role of T-cell-mediated inflammation in psoriasis: pathogenesis and targeted therapy

Psoriasis is one of the most common chronic, inflammatory, T-cell-mediated autoimmune diseases. Over the past decade, increased knowledge of disease pathogenesis has fundamentally changed psoriasis treatment, with the introduction of biologics, and this has led to a multitude of improved selective targets providing potential therapeutic options. Indeed, numerous pathogenesis-based treatments are currently in development, as psoriasis has also become increasingly relevant for proof-of-concept studies. The purpose of this review was to summarize current knowledge of psoriasis immunopathogenesis, focusing on the T-cell-mediated immune response and its initiation. The authors describe recent advances in psoriasis treatment and discuss pathogenesis-based therapies that are currently in development or which could be envisioned for the future. Although current biologics are well tolerated, several issues such as long-term efficacy, long-term safety, and high costs keep driving the search for new and better therapies. With further advances in understanding disease pathogenesis, more genomic data from psoriasis patients becoming available, and potentially the identification of autoantigens in psoriasis, current research should lead to the development of a growing arsenal of improved targeted treatments and to further breakthrough immunotherapies.

The roles of granulocyte-macrophage colony-stimulating factor and interleukin 3 in stromal cell-mediated hemopoiesis in vivo.

Adherent cells from murine long-term marrow cultures (LTMC) were examined for presence of mRNA for granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin 3 (Il-3). Six hours after medium replacement, GM-CSF mRNA was detected but was no longer detectable 24 h after feeding; Il-3 mRNA was not detected at any time. Neutralizing antibodies against these factors had no effect on hemopoiesis. Exogenous Il-3 increased cell production, notably mature erythroid progenitors, whereas GM-CSF had little long-term effect even at high concentrations. Furthermore, GM-CSF appeared to be specifically removed from the medium, whereas virtually all of the Il-3 could be recovered under identical incubation conditions. These results show that Il-3 is not required for maintaining long-term hemopoiesis in vitro, whereas the precise role of GM-CSF in this system remains unclear.

CCL17 Promotes Intestinal Inflammation in Mice and Counteracts Regulatory T Cell-Mediated Protection From Colitis.

BACKGROUND & AIMS: Priming of T cells by dendritic cells (DCs) in the intestinal mucosa and associated lymphoid tissues helps maintain mucosal tolerance but also contributes to the development of chronic intestinal inflammation. Chemokines regulate the intestinal immune response and can contribute to pathogenesis of inflammatory bowel diseases. We investigated the role of the chemokine CCL17, which is expressed by conventional DCs in the intestine and is up-regulated during colitis. METHODS: Colitis was induced by administration of dextran sodium sulfate (DSS) to mice or transfer of T cells to lymphopenic mice. Colitis activity was monitored by body weight assessment, histologic scoring, and cytokine profile analysis. The direct effects of CCL17 on DCs and the indirect effects on differentiation of T helper (Th) cells were determined in vitro and ex vivo. RESULTS: Mice that lacked CCL17 (Ccl17(E/E) mice) were protected from induction of severe colitis by DSS or T-cell transfer. Colonic mucosa and mesenteric lymph nodes from Ccl17-deficient mice produced lower levels of proinflammatory cytokines. The population of Foxp3(+) regulatory T cells (Tregs) was expanded in Ccl17(E/E) mice and required for long-term protection from colitis. CCR4 expression by transferred T cells was not required for induction of colitis, but CCR4 expression by the recipients was required. CCL17 promoted Toll-like receptor-induced secretion of interleukin-12 and interleukin-23 by DCs in an autocrine manner, promoted differentiation of Th1 and Th17 cells, and reduced induction of Foxp3(+) Treg cells. CONCLUSIONS: The chemokine CCL17 is required for induction of intestinal inflammation in mice. CCL17 has an autocrine effect on DCs that promotes production of inflammatory cytokines and activation of Th1 and Th17 cells and reduces expansion of Treg cells.

Blocking the B7-H4 pathway with novel recombinant antibodies enhances T cell-mediated antitumor responses.

B7-H4 inhibits T-cell activation and is widely expressed by solid neoplasms. We have recently demonstrated that the expression of B7-H4 on the surface of malignant cells in vivo is inducible, and that novel anti-B7-H4 recombinant antibodies can reverse the inhibition of tumor-specific T cells. Thus, antibodies targeting the B7-H4 pathways may extend the survival of cancer patients by restoring T cell-mediated antitumor responses.

The human T cell response to melanoma antigens.

The cornerstone of the concept of immunosurveillance in cancer should be the experimental demonstration of immune responses able to alter the course of in vivo spontaneous tumor progression. Elegant genetic manipulation of the mouse immune system has proved this tenet. In parallel, progress in understanding human T cell mediated immunity has allowed to document the existence in cancer patients of naturally acquired T cell responses to molecularly defined tumor antigens. Various attributes of cutaneous melanoma tumors, notably their adaptability to in vitro tissue culture conditions, have contributed to convert this tumor in the prototype for studies of human antitumor immune responses. As a consequence, the first human cytolytic T lymphocyte (CTL)-defined tumor antigen and numerous others have been identified using lymphocyte material from patients bearing this tumor, detailed analyses of specific T cell responses have been reported and a relatively large number of clinical trials of vaccination have been performed in the last 15 years. Thus, the "melanoma model" continues to provide valuable insights to guide the development of clinically effective cancer therapies based on the recruitment of the immune system. This chapter reviews recent knowledge on human CD8 and CD4 T cell responses to melanoma antigens.

Ipilimumab-dependent cell-mediated cytotoxicity of regulatory T cells ex vivo by nonclassical monocytes in melanoma patients.

Enhancing immune responses with immune-modulatory monoclonal antibodies directed to inhibitory immune receptors is a promising modality in cancer therapy. Clinical efficacy has been demonstrated with antibodies blocking inhibitory immune checkpoints such as cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) or PD-1/PD-L1. Treatment with ipilimumab, a fully human CTLA-4-specific mAb, showed durable clinical efficacy in metastatic melanoma; its mechanism of action is, however, only partially understood. This is a study of 29 patients with advanced cutaneous melanoma treated with ipilimumab. We analyzed peripheral blood mononuclear cells (PBMCs) and matched melanoma metastases from 15 patients responding and 14 not responding to ipilimumab by multicolor flow cytometry, antibody-dependent cell-mediated cytotoxicity (ADCC) assay, and immunohistochemistry. PBMCs and matched tumor biopsies were collected 24 h before (i.e., baseline) and up to 4 wk after ipilimumab. Our findings show, to our knowledge for the first time, that ipilimumab can engage ex vivo FcγRIIIA (CD16)-expressing, nonclassical monocytes resulting in ADCC-mediated lysis of regulatory T cells (Tregs). In contrast, classical CD14(++)CD16(-) monocytes are unable to do so. Moreover, we show that patients responding to ipilimumab display significantly higher baseline peripheral frequencies of nonclassical monocytes compared with nonresponder patients. In the tumor microenvironment, responders have higher CD68(+)/CD163(+) macrophage ratios at baseline and show decreased Treg infiltration after treatment. Together, our results suggest that anti-CTLA-4 therapy may target Tregs in vivo. Larger translational studies are, however, warranted to substantiate this mechanism of action of ipilimumab in patients.

Identifying Individual T Cell Receptors of Optimal Avidity for Tumor Antigens.

Cytotoxic T cells recognize, via their T cell receptors (TCRs), small antigenic peptides presented by the major histocompatibility complex (pMHC) on the surface of professional antigen-presenting cells and infected or malignant cells. The efficiency of T cell triggering critically depends on TCR binding to cognate pMHC, i.e., the TCR-pMHC structural avidity. The binding and kinetic attributes of this interaction are key parameters for protective T cell-mediated immunity, with stronger TCR-pMHC interactions conferring superior T cell activation and responsiveness than weaker ones. However, high-avidity TCRs are not always available, particularly among self/tumor antigen-specific T cells, most of which are eliminated by central and peripheral deletion mechanisms. Consequently, systematic assessment of T cell avidity can greatly help distinguishing protective from non-protective T cells. Here, we review novel strategies to assess TCR-pMHC interaction kinetics, enabling the identification of the functionally most-relevant T cells. We also discuss the significance of these technologies in determining which cells within a naturally occurring polyclonal tumor-specific T cell response would offer the best clinical benefit for use in adoptive therapies, with or without T cell engineering.

N-WASP is required for B-cell-mediated autoimmunity in Wiskott-Aldrich syndrome.

Mutations of the Wiskott-Aldrich syndrome gene (WAS) are responsible for Wiskott-Aldrich syndrome (WAS), a disease characterized by thrombocytopenia, eczema, immunodeficiency, and autoimmunity. Mice with conditional deficiency of Was in B lymphocytes (B/WcKO) have revealed a critical role for WAS protein (WASP) expression in B lymphocytes in the maintenance of immune homeostasis. Neural WASP (N-WASP) is a broadly expressed homolog of WASP, and regulates B-cell signaling by modulating B-cell receptor (BCR) clustering and internalization. We have generated a double conditional mouse lacking both WASP and N-WASP selectively in B lymphocytes (B/DcKO). Compared with B/WcKO mice, B/DcKO mice showed defective B-lymphocyte proliferation and impaired antibody responses to T-cell-dependent antigens, associated with decreased autoantibody production and lack of autoimmune kidney disease. These results demonstrate that N-WASP expression in B lymphocytes is required for the development of autoimmunity of WAS and may represent a novel therapeutic target in WAS.

NLRC5 shields T lymphocytes from NK-cell-mediated elimination under inflammatory conditions.

NLRC5 is a transcriptional regulator of MHC class I (MHCI), which maintains high MHCI expression particularly in T cells. Recent evidence highlights an important NK-T-cell crosstalk, raising the question on whether NLRC5 specifically modulates this interaction. Here we show that NK cells from Nlrc5-deficient mice exhibit moderate alterations in inhibitory receptor expression and responsiveness. Interestingly, NLRC5 expression in T cells is required to protect them from NK-cell-mediated elimination upon inflammation. Using T-cell-specific Nlrc5-deficient mice, we show that NK cells surprisingly break tolerance even towards 'self' Nlrc5-deficient T cells under inflammatory conditions. Furthermore, during chronic LCMV infection, the total CD8(+) T-cell population is severely decreased in these mice, a phenotype reverted by NK-cell depletion. These findings strongly suggest that endogenous T cells with low MHCI expression become NK-cell targets, having thus important implications for T-cell responses in naturally or therapeutically induced inflammatory conditions.

Narcolepsy-Associated HLA Class I Alleles Implicate Cell-Mediated Cytotoxicity.

STUDY OBJECTIVES: Narcolepsy with cataplexy is tightly associated with the HLA class II allele DQB1*06:02. Evidence indicates a complex contribution of HLA class II genes to narcolepsy susceptibility with a recent independent association with HLA-DPB1. The cause of narcolepsy is supposed be an autoimmune attack against hypocretin-producing neurons. Despite the strong association with HLA class II, there is no evidence for CD4+ T-cell-mediated mechanism in narcolepsy. Since neurons express class I and not class II molecules, the final effector immune cells involved might include class I-restricted CD8+ T-cells. METHODS: HLA class I (A, B, and C) and II (DQB1) genotypes were analyzed in 944 European narcolepsy with cataplexy patients and in 4,043 control subjects matched by country of origin. All patients and controls were DQB1*06:02 positive and class I associations were conditioned on DQB1 alleles. RESULTS: HLA-A*11:01 (OR = 1.49 [1.18-1.87] P = 7.0*10(-4)), C*04:01 (OR = 1.34 [1.10-1.63] P = 3.23*10(-3)), and B*35:01 (OR = 1.46 [1.13-1.89] P = 3.64*10(-3)) were associated with susceptibility to narcolepsy. Analysis of polymorphic class I amino-acids revealed even stronger associations with key antigen-binding residues HLA-A-Tyr(9) (OR = 1.32 [1.15-1.52] P = 6.95*10(-5)) and HLA-C-Ser(11) (OR = 1.34 [1.15-1.57] P = 2.43*10(-4)). CONCLUSIONS: Our findings provide a genetic basis for increased susceptibility to infectious factors or an immune cytotoxic mechanism in narcolepsy, potentially targeting hypocretin neurons.

Ecological and physiological variance in T-cell mediated immune response in Cory's shearwaters

T-cell mediated immune response (CMI) hasbeen widely studied in relation to individual andfitness components in birds. However, few studieshave simultaneously examined individual and socialfactors and habitat-mediated variance in theimmunity of chicks and adults from the samepopulation and in the same breeding season. Weinvestigated ecological and physiological variancein CMI of male and female nestlings and adults in abreeding population of Cory's Shearwaters(Calonectrisdiomedea) in theMediterranean Sea. Explanatory variables includedindividual traits (body condition, carbon andnitrogen stable isotope ratios, plasma totalproteins, triglycerides, uric acid, osmolarity,β-hydroxy-butyrate, erythrocyte meancorpuscular diameter, hematocrit, andhemoglobin) and burrow traits(temperature, isolation, and physicalstructure). During incubation, immune responseof adult males was significantly greater than thatof females. Nestlings exhibited a lower immuneresponse than adults. Ecological and physiologicalfactors affecting immune response differed betweenadults and nestlings. General linear models showedthat immune response in adult males was positivelyassociated with burrow isolation, suggesting thatmales breeding at higher densities suffer immunesystem suppression. In contrast, immune response inchicks was positively associated with bodycondition and plasma triglyceride levels.Therefore, adult immune response appears to beassociated with social stress, whereas a trade-offbetween immune function and fasting capability mayexist for nestlings. Our results, and those fromprevious studies, provide support for anasymmetrical influence of ecological andphysiological factors on the health of differentage and sex groups within a population, and for theimportance of simultaneously considering individualand population characteristics in intraspecificstudies of immune response.