Loss of Treg function appears to be a critical factor in the pathogenesis of human autoimmune diseases. Attention has focused on defects of CD4 + CD25 high Tregs, and techniques have been developed to determine their function. In contrast, the role of Tr1 regulatory T cells, which secrete the antiinflammatory cytokine IL-10, in autoimmune disease has not been well assessed. CD46 is a newly defined costimulatory molecule for T cell activation, and CD46-costimulated human T cells induce a Tr1 Treg phenotype with considerable amounts of IL-10 secretion. Here, we examined the role of Tr1 cells in patients with multiple sclerosis (MS) by stimulating CD4 + T cells with anti-CD3 and -CD46 mAbs and measuring IL-10 secretion. There were striking defects in the induction of Tr1 cells with CD46 costimulation as measured by IL-10 but not IFN-γ secretion in patients with MS compared with healthy subjects. This loss of Tr1 cell-associated IL-10 secretion was specific to CD46 and not CD28 costimulation and was associated with an altered regulation of the CD46-Cy2 isoform that differentially regulates T cell function in a CD46-transgenic murine model. These data demonstrate a second major Treg defect in human autoimmune disease associated with the CD46 pathway.

Integrin ligation initiates intracellular signaling events, among which are the activation of protein tyrosine kinases. The related adhesion focal tyrosine kinase (RAFTK), also known as PYK2 and CAKbeta, is a tyrosine kinase that is homologous to the focal adhesion kinase (FAK) p125FAK. The structure of RAFTK is similar to p125FAK in that it lacks a transmembrane region, does not contain Src homology 2 or 3 domains, and has a proline-rich region in its C terminus. Here we report that RAFTK is a target for beta1-integrin-mediated tyrosine phosphorylation in both transformed and normal human B cells. Ligation of the B cell antigen receptor also induced tyrosine phosphorylation of RAFTK. Phosphorylation of RAFTK following integrin- or B cell antigen receptor-mediated stimulation was decreased by prior treatment of cells with cytochalasin B, indicating that this process was at least partially cytoskeleton-dependent. One of the tyrosine-phosphorylated substrates after integrin stimulation in fibroblasts is p130cas, which can associate with p125FAK. RAFTK also interacted constitutively with p130cas in B cells, since p130cas was detected in RAFTK immunoprecipitates. Although the function of RAFTK remains unknown, these data suggest that RAFTK may have a significant function in integrin-mediated signaling pathways in B cells.

SummaryInfection by helminth parasites is associated with amelioration of allergic reactivity, but mechanistic insights into this association are lacking. Products secreted by the mouse parasite Heligmosomoides polygyrus suppress type 2 (allergic) immune responses through interference in the interleukin-33 (IL-33) pathway. Here, we identified H. polygyrus Alarmin Release Inhibitor (HpARI), an IL-33-suppressive 26-kDa protein, containing three predicted complement control protein (CCP) modules. In vivo, recombinant HpARI abrogated IL-33, group 2 innate lymphoid cell (ILC2) and eosinophilic responses to Alternaria allergen administration, and diminished eosinophilic responses to Nippostrongylus brasiliensis, increasing parasite burden. HpARI bound directly to both mouse and human IL-33 (in the cytokine’s activated state) and also to nuclear DNA via its N-terminal CCP module pair (CCP1/2), tethering active IL-33 within necrotic cells, preventing its release, and forestalling initiation of type 2 allergic responses. Thus, HpARI employs a novel molecular strategy to suppress type 2 immunity in both infection and allergy.

CD46 is a widely expressed transmembrane protein that was initially identified as binding and inactivating C3b and C4b complement products. We used mice that were transgenic for one of two human CD46 isoforms that differ in their cytoplasmic domains (termed CD46-1 and CD46-2) to analyze the effect of CD46 stimulation on the immune response. We show here that CD46 can regulate inflammatory responses, either by inhibiting (CD46-1) or increasing (CD46-2) the contact hypersensitivity reaction. We found that engagement of CD46-1 or CD46-2 differentially affected CD8(+) T cell cytotoxicity, CD4(+) T cell proliferation, interleukin 2 (IL-2) and IL-10 production as well as tyrosine phosphorylation of Vav in T lymphocytes. These results indicate that CD46 plays a role in regulating the T cell induced inflammatory reaction and in fine-tuning the cellular immune response by bridging innate and acquired immunity.

The widely expressed transmembrane molecule CD46 is the complement regulatory receptor for C3b as well as the receptor for several pathogens. Beside its binding functions, CD46 is also able to transduce signals. We showed that CD46 aggregation on human T cells induces p120CBL and linker for activation of T cells (LAT) phosphorylation. These two proteins are adaptor proteins known to regulate TCR signaling. p120CBL is a complex adaptor protein involved in negatively regulating signaling events, whereas LAT is a transmembrane adaptor protein found in glycolipid-enriched microdomains essential for T cell activation. Therefore, we investigated if a CD46/TCR costimulation would affect T cell activation. Indeed, CD46/CD3 costimulation strongly promotes T cell proliferation. Therefore, we propose that CD46 acts as a potent costimulatory molecule for human T cells.

1 Statins inhibit synthesis of mevalonate, a precursor of ubiquinone that is a central compound of the mitochondrial respiratory chain. The main adverse effect of statins is a toxic myopathy possibly related to mitochondrial dysfunction. 2 This study was designed to evaluate the effect of lipid-lowering drugs on ubiquinone (coenzyme Q10 ) serum level and on mitochondrial function assessed by blood lactate/pyruvate ratio. 3 Eighty hypercholesterolaemic patients (40 treated by statins, 20 treated by fibrates, and 20 untreated patients, all 80 having total cholesterol levels >6.0 mmol l−1) and 20 healthy controls were included. Ubiquinone serum level and blood lactate/pyruvate ratio used as a test for mitochondrial dysfunction were evaluated in all subjects. 4 Lactate/pyruvate ratios were significantly higher in patients treated by statins than in untreated hypercholesterolaemic patients or in healthy controls (P<0.05 and P<0.001). The difference was not significant between fibratetreated patients and untreated patients. 5 Ubiquinone serum levels were lower in statin-treated patients (0.75 mg l−1±0.04) than in untreated hypercholesterolaemic patients ( 0.95 mg l−1±0.09; P<0.05). 6 We conclude that statin therapy can be associated with high blood lactate/ pyruvate ratio suggestive of mitochondrial dysfunction. It is uncertain to what extent low serum levels of ubiquinone could explain the mitochondrial dysfunction.

The Crk-associated substrate p130 Cas (Cas) and the recently described human enhancer of filamentation 1 (HEF1) are two proteins with similar structure (64% amino acid homology), which are thought to act as "docking" molecules in intracellular signaling cascades.

Measles virus infection induces a profound immunosuppression that can lead to serious secondary infections. Here we demonstrate that measles virus induces tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) mRNA and protein expression in human monocyte-derived dendritic cells. Moreover, measles virusinfected dendritic cells are shown to be cytotoxic via the TRAIL pathway.Secondary infections due to a marked immunosuppression have long been recognized as a major cause of the high morbidity and mortality rates associated with measles virus (MV) infection. The mechanisms underlying the inhibition of cellmediated immunity following MV infection are not clearly understood, but dysfunction of MV-infected monocytes (7, 9, 10) and dendritic cells (DCs) as antigen-presenting cells (3, 5, 12) has been described. In previous work, we demonstrated induction of T-cell apoptosis by MV-infected DCs (3). To account for this killer activity of MV-infected DCs, we investigated tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) expression in human monocyte-derived DCs after MV infection. TRAIL is a type II transmembrane protein that was initially identified based on the homology of its extracellular domain with those of TNF family members (15). TRAIL does not seem to be cytotoxic toward normal cells but induces apoptosis of a wide variety of transformed cell lines (6,14). Moreover, T cells from human immunodeficiency virus (HIV) type 1-infected patients, which were previously shown to exhibit increased Fas sensitivity, are even more susceptible to TRAIL-induced cell death (6,8). These data suggest that TRAIL may participate in apoptosis of lymphoid cells and that it may be involved in dysregulated apoptosis following infection by immunosuppressive viruses such as HIV type 1. Here we demonstrate for the first time that functional TRAIL is produced by MV-infected DCs and mediates their cytotoxic activity.DCs were obtained from purified peripheral blood monocytes cultured for 6 days in the presence of granulocyte-macrophage colony-stimulating factor and interleukin-4 as previously described (3). DCs were infected with 1 PFU of Vero cell-derived MV (Edmonston strain) per cell for 3 h at 37°C, then washed and placed in culture. Cells were harvested 4, 8, 12, and 24 h after infection, and total RNA was extracted. TRAIL mRNA expression was quantified by an RNase protection assay (Riboquant hApo3) in accordance with the manufacturer's (PharMingen, San Diego, Calif.) specifications. As shown in Fig. 1A