Extracellular vesicles from pristane-treated CD38-deficient mice express an anti-inflammatory neutrophil protein signature, which reflects the mild lupus severity elicited in these mice

In CD38-deficient (Cd38-/-) mice intraperitoneal injection of pristane induces a lupus-like disease, which is milder than that induced in WT mice, showing significant differences in the inflammatory and autoimmune processes triggered by pristane. Extracellular vesicles (EV) are present in all body fluids. Shed by cells, their molecular make-up reflects that of their cell of origin and/or tissue pathological situation. The aim of this study was to analyze the protein composition, protein abundance, and functional clustering of EV released by peritoneal exudate cells (PECs) in the pristane experimental lupus model, to identify predictive or diagnostic biomarkers that might discriminate the autoimmune process in lupus from inflammatory reactions and/or normal physiological processes. In this study, thanks to an extensive proteomic analysis and powerful bioinformatics software, distinct EV subtypes were identified in the peritoneal exudates of pristane-treated mice: 1) small EV enriched in the tetraspanin CD63 and CD9, which are likely of exosomal origin; 2) small EV enriched in CD47 and CD9, which are also enriched in plasma-membrane, membrane-associated proteins, with an ectosomal origin; 3) small EV enriched in keratins, ECM proteins, complement/coagulation proteins, fibrin clot formation proteins, and endopetidase inhibitor proteins. This enrichment may have an inflammation-mediated mesothelial-to-mesenchymal transition origin, representing a protein corona on the surface of peritoneal exudate EV; 4) HDL-enriched lipoprotein particles. Quantitative proteomic analysis allowed us to identify an anti-inflammatory, Annexin A1-enriched pro-resolving, neutrophil protein signature, which was more prominent in EV from pristane-treated Cd38-/- mice, and quantitative differences in the protein cargo of the ECM-enriched EV from Cd38-/- vs WT mice. These differences are likely to be related with the distinct inflammatory outcome shown by Cd38-/- vs WT mice in response to pristane treatment. Our results demonstrate the power of a hypothesis-free and data-driven approach to transform the heterogeneity of the peritoneal exudate EV from pristane-treated mice in valuable information about the relative proportion of different EV in a given sample and to identify potential protein markers specific for the different small EV subtypes, in particular those proteins defining EV involved in the resolution phase of chronic inflammation.

CD38 Deficiency Ameliorates Chronic Graft-Versus-Host Disease Murine Lupus via a B-Cell-Dependent Mechanism

The absence of the mouse cell surface receptor CD38 in Cd38^−/− mice suggests that this receptor acts as a positive regulator of inflammatory and autoimmune responses. Here, we report that, in the context of the chronic graft-versus-host disease (cGVHD) lupus inducible model, the transfer of B6.C-H2bm12/KhEg(bm12) spleen cells into co-isogenic Cd38^−/− B6 mice causes milder lupus-like autoimmunity with lower levels of anti-ssDNA autoantibodies than the transfer of bm12 spleen cells into WT B6 mice. In addition, significantly lower percentages of Tfh cells, as well as GC B cells, plasma cells, and T-bet⁺CD11c^hi B cells, were observed in Cd38^−/− mice than in WT mice, while the expansion of Treg cells and Tfr cells was normal, suggesting that the ability of Cd38^−/− B cells to respond to allogeneic help from bm12 CD4⁺ T cells is greatly diminished. The frequencies of T-bet⁺CD11c^hi B cells, which are considered the precursors of the autoantibody-secreting cells, correlate with anti-ssDNA autoantibody serum levels, IL-27, and sCD40L. Proteomics profiling of the spleens from WT cGVHD mice reflects a STAT1-driven type I IFN signature, which is absent in Cd38^−/− cGVHD mice. Kidney, spleen, and liver inflammation was mild and resolved faster in Cd38^−/− cGVHD mice than in WT cGVHD mice. We conclude that CD38 in B cells functions as a modulator receptor that controls autoimmune responses.

Multifaceted effects of soluble human CD6 in experimental cancer models

Background

CD6 is a lymphocyte surface co-receptor physically associated with the T-cell receptor (TCR)/CD3 complex at the center of the immunological synapse. There, CD6 assists in cell-to-cell contact stabilization and modulation of activation/differentiation events through interaction with CD166/ALCAM (activated leukocyte cell adhesion molecule), its main reported ligand. While accumulating evidence is attracting new interest on targeting CD6 for therapeutic purposes in autoimmune disorders, little is known on its potential in cancer. In an attempt to elucidate the in vivo relevance of blocking CD6-mediated interactions in health and disease, we explored the consequences of expressing high circulating levels of a soluble form CD6 (sCD6) as a decoy receptor.

Methods

High sCD6 serum levels were achieved by using transgenic C57BL/6 mice expressing human sCD6 under the control of lymphoid-specific transcriptional elements (shCD6LckEμTg) or wild type either transduced with hepatotropic adeno-associated virus coding for mouse sCD6 or undergoing repeated infusions of recombinant human sCD6 protein. Characterization of sCD6-induced changes was performed by ex vivo flow cytometry and functional analyses of mouse lymphoid organ cells. The in vivo relevance of those changes was explored by challenging mice with subcutaneous or metastatic tumors induced by syngeneic cancer cells of different lineage origins.

Results

Through a combination of in vitro and in vivo studies, we show that circulating sCD6 expression induces defective regulatory T cell (Treg) generation and function, decreased CD166/ALCAM-mediated tumor cell proliferation/migration and impaired galectin-induced T-cell apoptosis, supporting the fact that sCD6 modulates antitumor lymphocyte effector function and tumorigenesis. Accordingly, sCD6 expression in vivo resulted in delayed subcutaneous tumor growth and/or reduced metastasis on challenge of mice with syngeneic cancer cells.

Conclusions

Evidence is provided for the disruption of CD6 receptor–ligand interactions as a feasible immunomodulatory approach in cancer.

Therapeutic Effects of Anti-Bone Morphogenetic Protein and Activin Membrane-Bound Inhibitor Treatment in Psoriasis and Arthritis

OBJECTIVE

The transforming growth factor β (TGFβ) inhibitor BAMBI (bone morphogenetic protein and activin membrane-bound inhibitor) has been shown to control differentiation of CD4+ T lymphocytes into either tolerogenic Treg cells or pathogenic Th17 cells, through the regulation of TGFβ and interleukin-2 (IL-2) signaling strength. The present study was undertaken to explore the potential beneficial effects of this strategy of pharmacologic inhibition using novel anti-BAMBI monoclonal antibodies (mAb) in different experimental murine models of chronic skin and joint inflammatory/autoimmune disease.

METHODS

Development of Saccharomyces cerevisiae mannan-induced psoriatic arthritis (MIP) (n = 18-30 mice per group), imiquimod-induced skin psoriasis (n = 20-30 mice per group), or type II collagen-induced arthritis (CIA) (n = 13-16 mice per group) was analyzed in a total of 2-5 different experiments with either wild-type (WT) or BAMBI-deficient B10.RIII mice that were left untreated or treated with mAb B101.37 (mouse IgG1 anti-BAMBI), a mouse IgG1 anti-TNP isotype control, anti-CD25, or anti-TGFβ mAb.

RESULTS

Treatment of normal mice with IgG1 anti-BAMBI mAb clone B101.37 led to expansion of Treg cells in vivo, and had both preventive and therapeutic effects in mice with MIP (each P < 0.05 versus controls). The conferred protection against disease progression was found to be mediated by Treg cells, which controlled the activation and expansion of pathogenic IL-17-producing cells, and was dependent on the level of TGFβ activity. Furthermore, treatment with B101.37 mAb blocked both the development of skin psoriasis induced by imiquimod and the development of CIA in mice (each P < 0.05 versus controls). Finally, pharmacologic inhibition of BAMBI with the IgM anti-BAMBI mAb B143.14 also potentiated the suppressive activity of Treg cells in vitro (P < 0.001 versus controls).

CONCLUSION

These results in murine models identify BAMBI as a promising new therapeutic target for chronic inflammatory diseases and other pathologic conditions modulated by Treg cells.

Analysis of DDT Residues in Soil by ELISA: An International Interlaboratory Study

An international interlaboratory study was conducted to determine the performance of a group of laboratories from developing and developed countries. The study used a commercial microwell ELISA on unknown samples spiked with different levels of DDT. The study design was based on Youden pairs and balanced replicates. Two soils, differing in particle size distributions, organic matter content, and cation-exchange capacities and thought to be DDT-free, were spiked at 5 DDT levels between 0.025 and 2 mg/kg. Nineteen laboratories in 17 countries took part in the collaborative trial; of these, the majority were modestly equipped laboratories in developing countries. Samples were analyzed without filtration or cleanup and using standards of pure DDT in methanol. Data were analyzed for repeatability and reproducibility, and average recoveries at the spike levels were calculated. Mean real recoveries for both soils were similar (103% for soil A and 100% for soil B), with values between 0.1 and 2 mg/kg DDT. Precision estimates were best in the linear working range of the assay (0.1–0.5 mg/kg DDT), with reproducibility relative standard deviations (RSDR) typically averaging about 38 and 46% near the upper and lower detection limits, respectively. Corresponding repeatability relative standard deviation (RSDr) values were 20–36% and 36–57%. Thus, even though much of the trial was performed under developing country conditions, performance statistics were similar to other reported results obtained with ELISAs on small molecules of agricultural importance, such as mycotoxins and pesticide and antibiotic residues.

Anti-IL17 treatment ameliorates Down syndrome phenotypes in mice

Down syndrome (DS) is characterized by structural and functional anomalies that are present prenatally and that lead to intellectual disabilities. Later in life, the cognitive abilities of DS individuals progressively deteriorate due to the development of Alzheimer's disease (AD)-associated neuropathology (i.e., β-amyloid (Aβ) plaques, neurofibrillary tangles (NFTs), neurodegeneration, synaptic pathology, neuroinflammation and increased oxidative stress). Increasing evidence has shown that among these pathological processes, neuroinflammation plays a predominant role in AD etiopathology. In AD mouse models, increased neuroinflammation appears earlier than Aβ plaques and NFTs, and in DS and AD models, neuroinflammation exacerbates the levels of soluble and insoluble Aβ species, favoring neurodegeneration. The Ts65Dn (TS) mouse, the most commonly used murine model of DS, recapitulates many alterations present in both DS and AD individuals, including enhanced neuroinflammation. In this study, we observed an altered neuroinflammatory milieu in the hippocampus of the TS mouse model. Pro-inflammatory mediators that were elevated in the hippocampus of this model included pro-inflammatory cytokine IL17A, which has a fundamental role in mediating brain damage in neuroinflammatory processes. Here, we analyzed the ability of an anti-IL17A antibody to reduce the neuropathological alterations that are present in TS mice during early neurodevelopmental stages (i.e., hippocampal neurogenesis and hypocellularity) or that are aggravated in later-life stages (i.e., cognitive abilities, cholinergic neuronal loss and increased cellular senescence, APP expression, Aβ peptide expression and neuroinflammation). Administration of anti-IL17 for 5 months, starting at the age of 7 months, partially improved the cognitive abilities of the TS mice, reduced the expression of several pro-inflammatory cytokines and the density of activated microglia and normalized the APP and Aβ_1-42 levels in the hippocampi of the TS mice. These results suggest that IL17-mediated neuroinflammation is involved in several AD phenotypes in TS mice and provide a new therapeutic target to reduce these pathological characteristics.

CD38 promotes pristane-induced chronic inflammation and increases susceptibility to experimental lupus by an apoptosis-driven and TRPM2-dependent mechanism

In this study, we investigated the role of CD38 in a pristane-induced murine model of lupus. CD38-deficient (Cd38-/-) but not ART2-deficient (Art2-/-) mice developed less severe lupus compared to wild type (WT) mice, and their protective phenotype consisted of (i) decreased IFN-I-stimulated gene expression, (ii) decreased numbers of peritoneal CCR2hiLy6Chi inflammatory monocytes, TNF-α-producing Ly6G+ neutrophils and Ly6Clo monocytes/macrophages, (iii) decreased production of anti-single-stranded DNA and anti-nRNP autoantibodies, and (iv) ameliorated glomerulonephritis. Cd38-/- pristane-elicited peritoneal exudate cells had defective CCL2 and TNF-α secretion following TLR7 stimulation. However, Tnf-α and Cxcl12 gene expression in Cd38-/- bone marrow (BM) cells was intact, suggesting a CD38-independent TLR7/TNF-α/CXCL12 axis in the BM. Chemotactic responses of Cd38-/- Ly6Chi monocytes and Ly6G+ neutrophils were not impaired. However, Cd38-/- Ly6Chi monocytes and Ly6Clo monocytes/macrophages had defective apoptosis-mediated cell death. Importantly, mice lacking the cation channel TRPM2 (Trpm2-/-) exhibited very similar protection, with decreased numbers of PECs, and apoptotic Ly6Chi monocytes and Ly6Clo monocytes/macrophages compared to WT mice. These findings reveal a new role for CD38 in promoting aberrant inflammation and lupus-like autoimmunity via an apoptosis-driven mechanism. Furthermore, given the implications of CD38 in the activation of TRPM2, our data suggest that CD38 modulation of pristane-induced apoptosis is TRPM2-dependent.

Bone Morphogenetic Protein and Activin Membrane-Bound Inhibitor, a Transforming Growth Factor β Rheostat That Controls Murine Treg Cell/Th17 Cell Differentiation and the Development of Autoimmune Arthritis by Reducing Interleukin-2 Signaling

OBJECTIVE

Transforming growth factor β (TGFβ) plays a prominent role in the establishment of immunologic tolerance, and mice lacking TGFβ1 die of multiorgan inflammation early in life. TGFβ controls the differentiation of CD4+ lymphocytes into Treg cells or proinflammatory Th17 cells. Although this dual capacity is modulated by the presence of additional cytokines around the activated cells, TGFβ also dissociates Th17/Treg cell differentiation in a dose-dependent manner by mechanisms still unknown. The purpose of this study was to explore the contribution of bone morphogenetic protein and activin membrane-bound inhibitor (BAMBI) to the modulation of TGFβ activity during the differentiation of CD4+ cells and in the control of immunologic tolerance in mice with collagen-induced arthritis (CIA).

METHODS

The in vitro and in vivo Treg cell and Th17 cell differentiation and the development of CIA were compared in wild-type mice and BAMBI-deficient mice.

RESULTS

BAMBI was induced after activation by TGFβ and fixed the appropriate intensity level of TGFβ signaling in CD4+ cells. Its deficiency protected mice against the development of CIA by a Treg cell- and TGFβ-dependent mechanism. Mechanistically, BAMBI was found to regulate CD25 expression and interleukin-2 (IL-2) signaling in Treg cells and in IL-2- and/or TGFβ-activated CD4+ cells and modulated Treg cell and Th17 cell differentiation both in vitro and in vivo.

CONCLUSION

Taken together, the results indicate that BAMBI is a component of a rheostat-like mechanism that, through the control of TGFβ and IL-2 signaling strength, regulates the differentiation of CD4+ lymphocytes and the development of autoimmune arthritis.

BAMBI is a negative regulator of humoral immune responses

BAMBI (Bone Morphogenetic Protein and Activin Membrane Bound Inhibitor) is a plasma membrane-associated negative regulator of TGFβ signaling. Using mice deficient in BAMBI and anti-BAMBI monoclonal antibodies, we have recently demonstrated the contribution of this TGFβ inhibitor to the regulation of CD4 T-cell differentiation into pathogenic TH17 cells and tolerogenic regulatory T cells. In the present study, we explored the possible involvement of BAMBI in the control of humoral immune responses. We demonstrated that BAMBI-KO mice developed increased antibody responses against T-independent antigens. In addition, these mutant mice also exhibited enhanced antibody responses against several T-dependent antigens administered by different routes and even in the absence of adjuvants. Using adoptive CD4 T-cell transfer experiments and double WT/BAMBI-KO bone marrow chimeric mice we showed that in the mutant mice, B cells exhibited intrinsic defects that improved their interaction with antigen-specific activated CD4 T cells and their subsequent activation and differentiation into germinal center B cells and antibody secreting cells. In fact, B cells from BAMBI-KO mice exhibited enhanced proliferative responses in vitro and expressed higher levels of surface molecules involved in CD4:B cell interactions. Finally, we demonstrated here that the enhanced T-dependent antibody responses observed in BAMBI-KO mice were reverted after long-term treatment with an anti-TGFβ monoclonal antibody. In conclusion, our present study described for the first time a negative role of BAMBI in the control of T-independent and Tdependent antibody responses through the regulation of TGFβ signaling.

BAMBI, a new molecular target in autoimmunity

We have previous demonstrated that BAMBI (BMP and Activin Membrane Bound Inhibitor) negatively regulates the functional differentiation of CD4 T cells into tolerogenic regulatory T-cells (Tregs) and positively the differentiation into pro-inflammatory TH17 cells. Accordingly, mice deficient in BAMBI are resistant against the development of collagen type II-induced arthritis (CIA). To analyze the therapeutic effects of BAMBI inhibition in normal mice in the development of autoimmunity, we developed new inhibitory mouse anti-mouse BAMBI mAbs. Treatment of B10RIII wild type (WT) mice with a high dose of a mouse IgG1 anti-mouse BAMBI mAb (clone B101.37; 2 mg/mice/week), but not with a low dose of B101.37 (0.3 mg/mice/week) or a high dose of an irrelevant IgG1 mAb (2 mg/mice/week), inhibited the development of CIA as efficiently as observed in B10RIII.BAMBI-KO mice.

We further explore the therapeutic potential of B101.37 in experimental models of psoriasis (Ps) and psoriasis arthritis (PsA). A single ip injection of mannan from Saccharomyces cerevisiae induces an acute inflammation resembling human Ps and PsA in B10RIII.WT but with a reduced severity in B10RIII.BAMBI-KO mice. Again, treatment of WT mice with B101.37, but not with an irrelevant IgG1 antibody, protects the animals against mannan-induced PsA and Ps by a Treg- and TGFβ-dependent mechanism. B101.37 also exhibits a therapeutic activity against mannan-induced PsA and Ps once the disease has been established. Similar results have been observed in a model of Ps induced after the topic administration of the TLR-7 agonist imiquimod. Altogether, our results demonstrate the beneficial effects of BAMBI inhibitors in the treatment of autoimmune skin and joint diseases.

Map3k8 Modulates Monocyte State and Atherogenesis in ApoE-/- Mice

OBJECTIVE

Map3k8 (Cot/Tpl2) activates the MKK1/2-ERK1/2, MAPK pathway downstream from interleukin-1R, tumor necrosis factor-αR, NOD-2R (nucleotide-binding oligomerization domain-like 2R), adiponectinR, and Toll-like receptors. Map3k8 plays a key role in innate and adaptive immunity and influences inflammatory processes by modulating the functions of different cell types. However, its role in atherogenesis remains unknown. In this study, we analyzed the role of this kinase in this pathology.

APPROACH AND RESULTS

We show here that Map3k8 deficiency results in smaller numbers of Ly6C^highCD11c^low and Ly6C^lowCD11c^high monocytes in ApoE^-/- mice fed a high-fat diet (HFD). Map3k8^-/-ApoE^-/- monocytes displayed high rates of apoptosis and reduced amounts of Nr4a1, a transcription factor known to modulate apoptosis in Ly6C^lowCD11c^high monocytes. Map3k8^-/-ApoE^-/- splenocytes and macrophages showed irregular patterns of cytokine and chemokine expression. Map3k8 deficiency altered cell adhesion and migration in vivo and decreased CCR2 expression, a determinant chemokine receptor for monocyte mobilization, on circulating Ly6C^highCD11c^low monocytes. Map3k8^-/-ApoE^-/- mice fed an HFD showed decreased cellular infiltration in the atherosclerotic plaque, with low lipid content. Lesions had similar size after Map3k8^+/+ApoE^-/- bone marrow transplant into Map3k8^-/-ApoE^-/- and Map3k8^+/+ApoE^-/- mice fed an HFD, whereas smaller plaques were observed after the transplantation of bone marrow lacking both ApoE and Map3k8.

CONCLUSIONS

Map3k8 decreases apoptosis of monocytes and enhances CCR2 expression on Ly6C^highCD11c^low monocytes of ApoE^-/- mice fed an HFD. These findings explain the smaller aortic lesions in ApoE^-/- mice with Map3k8^-/-ApoE^-/- bone marrow cells fed an HFD, supporting further studies of Map3k8 as an antiatherosclerotic target.

Modulation of autoimmune arthritis severity in mice by apolipoprotein E (ApoE) and cholesterol

Apolipoprotein E (ApoE) deficiency promoted an exacerbation of autoimmune arthritis in mice by inducing proinflammatory immune responses. In this study we analysed the contribution of hypercholesterolaemia and/or the absence of ApoE anti-inflammatory properties, unrelated to its function in the control of cholesterol metabolism, towards the acceleration of arthritis in these mutant animals. The induction and severity of collagen type II-induced arthritis (CIA) were compared for B10.RIII wild-type (WT), B10.RIII.ApoE^+/- , B10.RIII.ApoE^-/- and B10.RIII.low-density lipoprotein receptor (LDLR^-/- ) mice with different concentrations of circulating ApoE and cholesterol. A 50-70% reduction in serum levels of ApoE was observed in heterozygous B10.RIII.ApoE^+/- mice in comparison to B10.RIII.WT, although both strains of mice exhibited similar circulating lipid profiles. This ApoE reduction was associated with an increased CIA severity that remained lower than in homozygous B10.RIII.ApoE^-/- mice. An important rise in circulating ApoE concentration was observed in hypercholesterolaemic B10.RIII.LDLR^-/- mice fed with a normal chow diet, and both parameters increased further with an atherogenic hypercholesterolaemic diet. However, the severity of CIA in B10.RIII.LDLR^-/- mice was similar to that of B10.RIII.WT controls. In conclusion, by comparing the evolution of CIA between several strains of mutant mice with different levels of serum ApoE and cholesterol, our results demonstrate that both hypercholesterolaemia and ApoE regulate the intensity of in-vivo systemic autoimmune responses.

Context-dependent regulation of Th17-associated genes and IFNγ expression by the transcription factor NFAT5

Stress-activated transcription factors influence T-cell function in different physiopathologic contexts. NFAT5, a relative of nuclear factor κB and the calcineurin-activated NFATc transcription factors, protects mammalian cells from hyperosmotic stress caused by the elevation of extracellular sodium levels. In T cells exposed to hypernatremia, NFAT5 not only induces osmoprotective gene products but also cytokines and immune receptors, which raises the question of whether this factor could regulate other T-cell functions in osmostress-independent contexts. Here we have used mice with a conditional deletion of Nfat5 in mature T lymphocytes to explore osmostress-dependent and -independent functions of this factor. In vitro experiments with CD4 T cells stimulated in hyperosmotic medium showed that NFAT5 enhanced the expression of IL-2 and the Th17-associated gene products RORγt and IL-23R. By contrast, NFAT5-deficient CD4 T cells activated in vivo by anti-CD3 antibody exhibited a different activation profile and were skewed towards enhanced interferon γ (IFNγ) and IL-17 expression and attenuated Treg responses. Using a model of experimental colitis, we observed that mice lacking NFAT5 in T cells exhibited exacerbated intestinal colitis and enhanced expression of IFNγ in draining lymph nodes and colon. These results show that NFAT5 can modulate different T-cell responses depending on stress conditions and stimulatory context.

Selective Impairment of TH17-Differentiation and Protection against Autoimmune Arthritis after Overexpression of BCL2A1 in T Lymphocytes

The inhibition of apoptotic cell death in T cells through the dysregulated expression of BCL2 family members has been associated with the protection against the development of different autoimmune diseases. However, multiple mechanisms were proposed to be responsible for such protective effect. The purpose of this study was to explore the effect of the T-cell overexpression of BCL2A1, an anti-apoptotic BCL2 family member without an effect on cell cycle progression, in the development of collagen-induced arthritis. Our results demonstrated an attenuated development of arthritis in these transgenic mice. The protective effect was unrelated to the suppressive activity of regulatory T cells but it was associated with a defective activation of p38 mitogen-activated protein kinase in CD4⁺ cells after in vitro TCR stimulation. In addition, the in vitro and in vivo T_H17 differentiation were impaired in BCL2A1 transgenic mice. Taken together, we demonstrated here a previously unknown role for BCL2A1 controlling the activation of CD4⁺ cells and their differentiation into pathogenic proinflammatory T_H17 cells and identified BCL2A1 as a potential target in the control of autoimmune/inflammatory diseases.

CD6 modulates thymocyte selection and peripheral T cell homeostasis

Orta-Mascaró, Lozano, and collaborators provide the first analysis of CD6-deficient mice, showing that this molecule modulates T cell receptor signaling and the threshold for thymocyte and peripheral T cell subset selection.

The CD6 glycoprotein is a lymphocyte surface receptor putatively involved in T cell development and activation. CD6 facilitates adhesion between T cells and antigen-presenting cells through its interaction with CD166/ALCAM (activated leukocyte cell adhesion molecule), and physically associates with the T cell receptor (TCR) at the center of the immunological synapse. However, its precise role during thymocyte development and peripheral T cell immune responses remains to be defined. Here, we analyze the in vivo consequences of CD6 deficiency. CD6^−/− thymi showed a reduction in both CD4⁺ and CD8⁺ single-positive subsets, and double-positive thymocytes exhibited increased Ca²⁺ mobilization to TCR cross-linking in vitro. Bone marrow chimera experiments revealed a T cell–autonomous selective disadvantage of CD6^−/− T cells during development. The analysis of TCR-transgenic mice (OT-I and Marilyn) confirmed that abnormal T cell selection events occur in the absence of CD6. CD6^−/− mice displayed increased frequencies of antigen-experienced peripheral T cells generated under certain levels of TCR signal strength or co-stimulation, such as effector/memory (CD4⁺T_EM and CD8⁺T_CM) and regulatory (T reg) T cells. The suppressive activity of CD6^−/− T reg cells was diminished, and CD6^−/− mice presented an exacerbated autoimmune response to collagen. Collectively, these data indicate that CD6 modulates the threshold for thymocyte selection and the generation and/or function of several peripheral T cell subpopulations, including T reg cells.

[Recommendations for the use of methotrexate in patients with juvenile idiopathic arthritis]

OBJECTIVES

To develop a consensus document of recommendations for the use of methotrexate (MTX) in patients with juvenile idiopathic arthritis (JIA).

MATERIAL AND METHOD

A group of eleven experts proposed several clinical questions on the use of MTX in patients with JIA. A systematic review was conducted and the evidence and recommendations for each question were extracted. The results were discussed and validated by the experts in a work session to establish the final recommendations.

RESULTS

MTX is recommended as the first drug for inducing remission in JIA, and its indication should be made according to the clinical category of the patient. Prior to treatment, it is recommended to perform a complete blood count, including white cells, levels of liver enzymes, serum creatinine, and other analytical parameters according to specific risk factors. Treatment should be initiated with a dose of 10-15 mg/m(2)/week. In cases of uveitis or polyarthritis, an initial dose of 15 mg/m(2)/week should be considered. For a better bioavailability and tolerability, it is preferable to administer MTX parenterally if the dose is ≥15 mg/m(2)/week. It is necessary to periodically perform an analytical monitoring of the patient and to assess possible alterations in liver enzymes to make changes if necessary. Combinations with biological agents may be necessary, as well as the concomitant addition of folic or folinic acid.

CONCLUSIONS

This document describes the main recommendations for the appropriate use of MTX in JIA patients, according to scientific evidence and clinical experience.