Mutations in MAPKBP1 Cause Juvenile or Late-Onset Cilia-Independent Nephronophthisis.

Nephronophthisis (NPH), an autosomal-recessive tubulointerstitial nephritis, is the most common cause of hereditary end-stage renal disease in the first three decades of life. Since most NPH gene products (NPHP) function at the primary cilium, NPH is classified as a ciliopathy. We identified mutations in a candidate gene in eight individuals from five families presenting late-onset NPH with massive renal fibrosis. This gene encodes MAPKBP1, a poorly characterized scaffolding protein for JNK signaling. Immunofluorescence analyses showed that MAPKBP1 is not present at the primary cilium and that fibroblasts from affected individuals did not display ciliogenesis defects, indicating that MAPKBP1 may represent a new family of NPHP not involved in cilia-associated functions. Instead, MAPKBP1 is recruited to mitotic spindle poles (MSPs) during the early phases of mitosis where it colocalizes with its paralog WDR62, which plays a key role at MSP. Detected mutations compromise recruitment of MAPKBP1 to the MSP and/or its interaction with JNK2 or WDR62. Additionally, we show increased DNA damage response signaling in fibroblasts from affected individuals and upon knockdown of Mapkbp1 in murine cell lines, a phenotype previously associated with NPH. In conclusion, we identified mutations in MAPKBP1 as a genetic cause of juvenile or late-onset and cilia-independent NPH.

Mutations in TRAF3IP1/IFT54 reveal a new role for IFT proteins in microtubule stabilization.

Ciliopathies are a large group of clinically and genetically heterogeneous disorders caused by defects in primary cilia. Here we identified mutations in TRAF3IP1 (TNF Receptor-Associated Factor Interacting Protein 1) in eight patients from five families with nephronophthisis (NPH) and retinal degeneration, two of the most common manifestations of ciliopathies. TRAF3IP1 encodes IFT54, a subunit of the IFT-B complex required for ciliogenesis. The identified mutations result in mild ciliary defects in patients but also reveal an unexpected role of IFT54 as a negative regulator of microtubule stability via MAP4 (microtubule-associated protein 4). Microtubule defects are associated with altered epithelialization/polarity in renal cells and with pronephric cysts and microphthalmia in zebrafish embryos. Our findings highlight the regulation of cytoplasmic microtubule dynamics as a role of the IFT54 protein beyond the cilium, contributing to the development of NPH-related ciliopathies.

Bleomycin-induced lung injury in mice investigated by MRI: model assessment for target analysis.

Magnetic resonance imaging (MRI) has been used to follow the course of bleomycin-induced lung injury in mice and to investigate two knockout mouse lines with the aim of providing potential therapeutic targets. Bleomycin (0.25 mg/kg) was administered intranasally six times, once a day. MRI was carried out on spontaneously breathing animals up to day 70 after bleomycin. Neither cardiac nor respiratory gating was applied during image acquisition. A long lasting response following bleomycin has been detected by MRI in the lungs of male C57BL/6 mice. Histology showed that, from day 14-70 after bleomycin, fibrosis was the predominant component of the injury. Female C57BL/6 mice displayed a smaller response than males. Bleomycin-induced injury was significantly more pronounced in C57BL/6 than in Balb/C mice. MRI and histology demonstrated a protection against bleomycin insult in female heterozygous and male homozygous cancer Osaka thyroid kinase knockout animals. In contrast, no protection was seen in cadherin-11 knockout animals. In summary, MRI can quantify, in spontaneously breathing mice, bleomycin-induced lung injury. With the ability for repetitive measurements in the same animal, the technique is attractive for in vivo target analysis and compound profiling in this murine model.

Analysis of independent microarray datasets of renal biopsies identifies a robust transcript signature of acute allograft rejection.

Transcriptomics could contribute significantly to the early and specific diagnosis of rejection episodes by defining 'molecular Banff' signatures. Recently, the description of pathogenesis-based transcript sets offered a new opportunity for objective and quantitative diagnosis. Generating high-quality transcript panels is thus critical to define high-performance diagnostic classifier. In this study, a comparative analysis was performed across four different microarray datasets of heterogeneous sample collections from two published clinical datasets and two own datasets including biopsies for clinical indication, and samples from nonhuman primates. We characterized a common transcriptional profile of 70 genes, defined as acute rejection transcript set (ARTS). ARTS expression is significantly up-regulated in all AR samples as compared with stable allografts or healthy kidneys, and strongly correlates with the severity of Banff AR types. Similarly, ARTS were tested as a classifier in a large collection of 143 independent biopsies recently published by the University of Alberta. Results demonstrate that the 'in silico' approach applied in this study is able to identify a robust and reliable molecular signature for AR, supporting a specific and sensitive molecular diagnostic approach for renal transplant monitoring.

Follicle-stimulating hormone does not impact male bone mass in vivo or human male osteoclasts in vitro.

Bone loss in the elderly is mainly caused by osteoclast-induced bone resorption thought to be causally linked to the decline in estrogen and testosterone levels in females and males. Recently, involvement of follicle stimulating-hormone (FSH) in this process has been suggested to explain in part the etiology of the disease in females, whereas its role in males has never been examined. In this study, the direct impact of FSH on bone mass of 16-week-old C57BL/6J male mice by either daily intermittent application of 6 or 60 mug/kg of FSH or continuous delivery via miniosmotic pump of a dose of 6 mug/kg over the course of a month was assessed. Femoral peripheral quantitative computed tomographic and microcomputed tomographic analyses at 0, 2, and 4 weeks of FSH-treated mice did not reveal any differences in cancellous and cortical bone compared to sham-treated mice. FSH functionality was verified by demonstrating cAMP induction and activation of a cAMP-response element-containing reporter cell line by FSH. Furthermore, osteoclastogenesis from human mononuclear cell precursors and from RAW 264.7 cells was not affected by FSH (3, 10, 30 ng/mL) compared to control. No direct effect of FSH on gene regulation was observed by Affymetrix Gene Array on RAW 264.7 cells. Lastly, no expression of FSH receptor (FSHR) mRNA or FSHR was observed by quantitative polymerase chain reaction and Western blot in either human male osteoclasts or RAW 264.7 cells. These data show that FSH does not appear to modulate male bone mass regulation in vivo and does not act directly on osteoclastogenesis in vitro.

CD8+ T cells are effector cells of contact dermatitis to common skin allergens in mice.

Allergic contact dermatitis (ACD) to strong experimental haptens is mediated by specific CD8+ T cells. Here, we show that similar mechanisms occur for weak haptens, which comprise the vast majority of chemicals responsible for human ACD. We used a model of ACD, that is, the contact hypersensitivity reaction, to test for the allergenicity of three weak haptens involved in fragrance allergy. ACD to weak haptens could not be induced in normal mice. In contrast, mice acutely depleted in CD4+ T cells developed a typical ACD reaction to the three weak fragrance allergens that peaked 24 hours after challenge. Priming of CD8+ T cells was observed in draining lymph nodes 5 days after sensitization and development of ACD was associated with the infiltration of activated CD8+ T cells in the challenged skin. CD8+ T cells were effectors of the ACD reaction as in vivo treatment with depleting anti-CD8 mAbs abrogated the ACD responses and as purified CD8+ T cells could adoptively transfer ACD to naive recipients. In conclusion, our data demonstrate a dominant role of CD8+ T cells as initiators of ACD to weak haptens, and suggest that CD8+ T cells may represent potential targets for preventing or treating ACD.

[Allergic contact dermatitis: how to re-induce tolerance?]. / Eczéma allergique de contact: comment ré-induire une tolérance?

Allergic contact dermatitis (ACD) is a skin inflammatory disease mediated by activation of CD8+ cytotoxic T cells specific for haptens in contact with the skin. CD4+ T cells behave as both regulatory and tolerogenic cells since they down-regulate the skin inflammation in patients with ACD (regulation) and prevent the development of eczema (tolerance) in normal individuals. Thus, ACD corresponds to a breakdown of immune tolerance to haptens in contact with the skin. Several regulatory CD4+ T cell subsets (Treg), especially CD4+CD25+ natural Treg cells, are involved in immunological tolerance and regulation to haptens through the production of the immunosuppressive cytokines IL-10 and TGF-beta. Ongoing strategies to re-induce immune tolerance to haptens in patients with eczema include improvement of existing methods of tolerance induction (oral tolerance, low dose tolerance, allergen-specific immunotherapy, UV-induced tolerance) as well as development of new drugs able to activate IL-10 producing Treg cells in vivo. Ongoing and future progress in this area will open up new avenues for treatment of eczema and more generally autoimmune and allergic diseases resulting from a breakdown of tolerance to autoantigens and allergens, respectively.

Lysophosphatidylcholine is a natural adjuvant that initiates cellular immune responses.

The discovery of new adjuvants that can stimulate the immune response to protein antigens is a major issue for the development of subunit vaccines. Lipoprotein oxidation occurring during the acute phase response (APR) to aggression of the organism, provides signals of danger that are detected by dendritic cells (DC). Among other instructive molecules generated during the APR, lysophosphatidylcholine (LPC) promotes mature DC generation from differentiating human monocytes in vitro. It is shown here that LPC also controls the initiation of an adaptive immune response in vivo. LPC displays adjuvant properties when injected to mice in mixture with various antigens. Immunizations with LPC induced the production of antigen-specific antibodies with an efficiency similar to Alum, the reference adjuvant for human vaccination. Importantly, LPC also induced cytotoxic T cell responses, opening perspectives for vaccine development. Therefore, LPC is a natural adjuvant for the immune system, inducing humoral and cellular immune responses.

Fisiopatologia da dermatite de contato alérgica: papel das células T CD8 efetoras e das células T CD4 regulatórias / Update on the pathophysiology with special emphasis on CD8 effector T cells and CD4 regulatory T cells

A dermatite de contato alérgica (DCA), também conhecida como hipersensibilidade de contato (HSC) é uma das dermatoses inflamatórias mais freqüentes, sendo caracterizada por eritema, pápulas e vesículas, seguidas de ressecamento e descamação. A DCA é induzida pelo contato da pele com substâncias químicas não protéicas denominadas haptenos, e corresponde a uma reação de hipersensibilidade cutânea do tipo tardio, mediada por células T hapteno-específicas. Durante a fase de sensibilização, tanto os precursores de células T CD4+ quanto os de CD8+ são ativados nos linfonodos de drenagem através da apresentação de peptídeos conjugados a haptenos pelas células dendríticas (CD) da pele. A subseqüente exposição de pele ao hapteno em um local a distância induz o recrutamento e ativação de células T específicas no local de provocação, levando à apoptose dos queratinócitos, recrutamento de células inflamatórias e desenvolvimento de sintomas clínicos. Estudos experimentais dos últimos 10 anos demonstraram que, em respostas normais de HSC a haptenos fortes, as células T CD8+ do tipo 1 são efetoras da HSC através de citotoxicidade e produção de IFNgama, enquanto que as células T CD4+ são dotadas de funções de regulação negativa. Estas últimas podem corresponder à população de células T regulatórias CD4+ CD25+ recentemente descritas. Entretanto, em algumas situações, especialmente naquelas em que há um pool deficiente de células T CD8, as células T CD4+ podem ser efetoras da HSC. Estudos em andamento deverão confirmar que a fisiopatologia da DCA em humanos é semelhante à HSC em camundongos, e que a resposta de HSC a haptenos fracos comuns, mais freqüentemente envolvidos na DCA em humanos, é semelhante à descrita para haptenos fortes.

Exogenous and endogenous glycolipid antigens activate NKT cells during microbial infections.

CD1d-restricted natural killer T (NKT) cells are innate-like lymphocytes that express a conserved T-cell receptor and contribute to host defence against various microbial pathogens. However, their target lipid antigens have remained elusive. Here we report evidence for microbial, antigen-specific activation of NKT cells against Gram-negative, lipopolysaccharide (LPS)-negative alpha-Proteobacteria such as Ehrlichia muris and Sphingomonas capsulata. We have identified glycosylceramides from the cell wall of Sphingomonas that serve as direct targets for mouse and human NKT cells, controlling both septic shock reaction and bacterial clearance in infected mice. In contrast, Gram-negative, LPS-positive Salmonella typhimurium activates NKT cells through the recognition of an endogenous lysosomal glycosphingolipid, iGb3, presented by LPS-activated dendritic cells. These findings identify two novel antigenic targets of NKT cells in antimicrobial defence, and show that glycosylceramides are an alternative to LPS for innate recognition of the Gram-negative, LPS-negative bacterial cell wall.

Deficient contact hypersensitivity reaction in CD4-/- mice is because of impaired hapten-specific CD8+ T cell functions.

Mice deficient in the CD4 molecule (CD4-/-) are widely used to evaluate the requirement for CD4+ T cell help in viral, tumoral, and transplantation immunity. Previous studies, showing that CD4-/- mice develop impaired contact hypersensitivity (CHS) responses, have suggested that CD4+ T cells are required for the optimal induction of this skin inflammatory reaction. other studies have, however, demonstrated that CHS was mediated by CD8+ T cells, without the need for CD4+ T cell help. Here, we show that CD4-/- mice develop a normal delayed-type hypersensitivity response to protein antigen, which is mediated by major histocompatibility molecules class II-restricted CD4-CD8- T cells, but a decreased CHS response to 2,4-dinitro-fluorobenezene. Analysis of the hapten-specific T cell pool demonstrates that priming of CD8+ T cells occurred normally in CD4-/- mice, as assessed by specific proliferative responses and interferon-gamma (IFN-gamma) production of purified CD8+ T cells. Furthermore, CD8+ T cells were able to adoptively transfer a normal CHS reaction. In contrast, total lymph node cells from CD4-/- mice showed decreased IFN-gamma production and diminished specific cytotoxic T lymphocytes (CTL) activity, which could be reversed by in vitro restimulation with hapten-pulsed class II-deficient antigen-presenting cells. These data confirm that class I-restricted CD8+ T cells can fully develop in effectors of CHS in the absence of CD4+ T cell help and suggest that the impaired CHS in CD4-/- mice is because of the presence of a class II-restricted T cell subset, which controls CHS by inhibiting hapten-specific CTL responses.

Contribution of CD4(+ )and CD8(+) T-cells in contact hypersensitivity and allergic contact dermatitis.

Allergic contact dermatitis, also referred to as contact hypersensitivity, is one the most frequent inflammatory skin diseases, and is characterized by redness, papule and vesicles, followed by scaling and dryness. Allergic contact dermatitis is elicited upon skin contact with nonprotein chemicals, haptens, and corresponds to a cutaneous delayed type hypersensitivity reaction, mediated by hapten-specific T-cells. During the sensitization phase, both CD4(+) and CD8(+) T-cell precursors are activated in the draining lymph nodes by presentation of haptenated peptides by skin dendritic cells. Subsequent hapten painting on a remote skin site induces the recruitment and activation of specific T-cells at the site of challenge. This leads to apoptosis of keratinocytes, recruitment of inflammatory cells and development of clinical symptoms. Experimental studies from the last 10 years have demonstrated that, in normal contact hypersensitivity responses to strong haptens, CD8(+) type 1 T-cells are effector cells of contact hypersensitivity through cytotoxicity and interferon-gamma production, while CD4(+) T-cells are endowed with downregulatory functions. The latter may correspond to the recently described CD4(+)CD25(+) regulatory T-cell population. However, in some instances, especially when there is a deficient CD8(+) T-cell pool, CD4(+) T-cells can be effector cells of contact hypersensitivity. Ongoing studies will have to confirm that the pathophysiology of human allergic contact dermatitis is similar to the mouse contact hypersensitivity and that the contact hypersensitivity response to common weak haptens, most frequently involved in human allergic contact dermatitis, is similar to that reported for strong haptens.

Allergic contact dermatitis.

Contact dermatitis is an inflammatory skin condition induced by exposure to an environmental agent. Eczema and dermatitis are used synonymously to denote a polymorphous pattern of skin inflammation characterized at least in its acute phase by erythema, vesiculation and pruritus. Substances responsible for contact dermatitis after single or multiple exposures are non protein chemicals, i.e. haptens, that induce skin inflammation through activation of innate skin immunity (irritant contact dermatitis) or both innate and acquired specific immunity (allergic contact dermatitis). The present review will focus on allergic contact dermatitis, a delayed-type hypersensitivity reaction, which is mediated by hapten-specific T cells. Recent advances in the pathophysiology of ACD have shown that the occurrence of ACD, as well as its magnitude and duration, is controlled by the opposite functions of CD8 effector T cells and CD4 regulatory T cells. From these studies ACD can be considered as a breakdown of cutaneous immune tolerance to haptens.

The role of CD4+ and CD8+ T cells in contact hypersensitivity and allergic contact dermatitis.

Allergic contact dermatitis (ACD) and contact hypersensitivity (CHS) are delayed-type hypersensitivity reactions which are mediated by hapten specific T cells. During the sensitisation phases, both CD4+ and CD8+ T cell precursors are activated in the draining lymph nodes by presentation of haptenated peptides by skin dendritic cells. Subsequent hapten skin painting induces the recruitment of T cells at the site of challenge which induces inflammatory signals and apoptosis of epidermal cells, leading to the development of a skin inflammatory infiltrate and of clinical symptoms. There have been major controversies on the respective roles of CD4+ and CD8+ T cells in the development of the CHS inflammatory reaction. Experimental studies from the last 10 years have demonstrated that, in normal CHS responses to strong haptens, CD8+ type 1 T cells are effector cells of CHS while CD4+ T cells are endowed with down-regulatory functions. The latter may correspond to the recently described CD4+ CD25+ regulatory T cell population. However, in some instances, especially those where there is a deficient CD8 T cell pool, CD4+ T cells can be effector cells of CHS. Ongoing studies will have to confirm that the pathophysiology of human ACD is similar to the mouse CHS and that the CHS response to weak haptens, the most frequently involved in human ACD, is similar to that reported for strong haptens.

CD4+ T cells prevent skin autoimmunity during chronic autologous graft-versus-host-disease.

CD4 regulatory cells have been postulated to prevent autologous graft-vs.-host disease (GVHD). In order to test this hypothesis, we used BALB/c mice, a strain known to be resistant to autologous GVHD, which had received autologous stem cell transplantation (ASCT) and cyclosporine A (CsA). As expected, ASCT/CsA-treated BALB/c mice did not develop any sign of acute or chronic GVHD. However, depletion of CD4 T cells induced a skin disease with clinical and histological features of alopecia areata (AA), a CD8 T-cell-mediated human autoimmune skin disease. The hair loss in mice developing AA was associated with the infiltration of the skin by activated CD8 T cells. Analysis of the T-cell recovery in ASCT- and ASCT/CsA-treated mice showed that CsA induced an increase in the number of CD4+ 25+ T cells, suggesting that the lack of GVHD in ASCT/CsA treated-mice could be related to the expansion of this CD4 T-cell subset. Collectively these data show that CD4 T cells comprise regulatory cells controlling the onset of autologous GVHD and suggest that the naturally occurring CD4+ 25+ subset may be responsible for this effect.

Psychological stress exerts an adjuvant effect on skin dendritic cell functions in vivo.

Psychological stress affects the pathophysiology of infectious, inflammatory, and autoimmune diseases. However, the mechanisms by which stress could modulate immune responses in vivo are poorly understood. In this study, we report that application of a psychological stress before immunization exerts an adjuvant effect on dendritic cell (DC), resulting in increased primary and memory Ag-specific T cell immune responses. Acute stress dramatically enhanced the skin delayed-type hypersensitivity reaction to haptens, which is mediated by CD8(+) CTLs. This effect was due to increased migration of skin DCs, resulting in augmented CD8(+) T cell priming in draining lymph nodes and enhanced recruitment of CD8(+) T cell effectors in the skin upon challenge. This adjuvant effect of stress was mediated by norepinephrine (NE), but not corticosteroids, as demonstrated by normalization of the skin delayed-type hypersensitivity reaction and DC migratory properties following selective depletion of NE. These results suggest that release of NE by sympathetic nerve termini during a psychological stress exerts an adjuvant effect on DC by promoting enhanced migration to lymph nodes, resulting in increased Ag-specific T cell responses. Our findings may open new ways in the treatment of inflammatory diseases, e.g., psoriasis, allergic contact dermatitis, and atopic dermatitis.

IL-18 binding protein protects against contact hypersensitivity.

Allergic contact dermatitis, the clinical manifestation of contact hypersensitivity, is one of the most common disorders of the skin. It is elicited upon multiple cutaneous re-exposure of sensitized individuals to the sensitizing agent. In this study, we demonstrate that using IL-18 binding protein (IL-18BP) to neutralize IL-18 significantly reduced clinical symptoms in a murine model of contact hypersensitivity. Furthermore, IL-18BP alleviated the relapses during established disease, as indicated by significant protection during re-exposure of mice that had previously undergone a contact hypersensitivity response without treatment. Although edema was not influenced, IL-18BP reduced the number of T cells homing to sites of inflammation, resulting in diminished local production of IFN-gamma. Thus, by preventing the accumulation of effector T cells to the target tissue, IL-18BP appears to be a potent protective mediator to counter skin inflammation during contact hypersensitivity. Taken together with the evidence that IL-18 is present in tissue samples of the human disease, our data reinforces IL-18BP as a candidate for this therapeutic indication.

IL-2 therapy and thymic production of naive CD4 T cells in HIV-infected patients with severe CD4 lymphopenia.

OBJECTIVES: IL-2 therapy increases memory and naive CD4 T cells in HIV-infected patients, but its effect on thymopoiesis is unknown. To investigate this effect, we quantified T-cell receptor rearrangement excision circles (TREC) in CD4 T cells from lymphopenic AIDS patients treated with highly active antiretroviral therapy and IL-2. METHODS: CD4 cell subsets were evaluated by flow cytometry using anti-CD45RO/RA, CD62L, Ki67 and CD95 monoclonal antibodies. The proportion of recent thymic emigrant had been quantified by a real-time polymerase chain reaction assay for signal joint TREC in peripheral blood mononuclear and purified CD4 T cells. RESULTS: At initiation of IL-2, TREC copies/microl of blood were correlated with naive T cell numbers and age. Both naive and TREC numbers/microl significantly increased over time in all patients, with a wide range of TREC increases. Higher percentages of CD4+CD45RO-negative cells positive for the Ki67 cell-cycle marker were found in patients with a low TREC increase, but remained stable under IL-2. TREC and naive cell recovery were correlated; they also correlated with the numbers of TREC and naive cells at the start of IL-2, and with age, suggesting a thymic origin for naive T-cell recovery. A mathematical model showing the linear recovery of naive cells and TREC under IL-2 also strongly suggested that a naive T-cell increase reflects thymic export and involves little net death and proliferation. CONCLUSION: Although we cannot rule out a mechanism of altered proliferation or death rate, the thymus plays an important role in the long-term recovery of naive T cells under IL-2 therapy.

Immunosuppressive antimetabolites inhibit induction of contact hypersensitivity while lymphoablative drugs also prevent its expression.

Contact hypersensitivity is one of the most common skin diseases and its pharmacological control is an important clinical issue. We investigated the control of contact hypersensitivity by immunosuppressive drugs administered during sensitization or challenge. Mycophenolate mofetil, methotrexate and 5-fluorouracil completely inhibited contact hypersensitivity when administered during sensitization whereas they did not decrease inflammatory reaction when administered during challenge. Conversely, mitoxantrone, and cyclophosphamide, given as a single injection at the time of sensitization or challenge, completely inhibited the reaction, a property associated with T and B cell depletion. The data indicate that antimetabolites which are cell cycle dependent inhibit clonal expansion and subsequent differentiation of cytotoxic CD8+ T cells. Their lack of effect at the time of challenge indicates that T cell proliferation is not required for the expression of effector or regulatory T cell activation. Conversely lymphoablative drugs can inactivate or destroy differentiated cytotoxic T cells with rapid kinetics.