Recent studies have demonstrated that in peripheral lymphoid tissues of normal mice and healthy humans, 1% to 5% of αβ T-cell receptor–positive (TCR+) T cells are CD4−CD8− (double-negative [DN]) T cells, capable of down-regulating immune responses. However, the origin and developmental pathway of DN T cells is still not clear. In this study, by monitoring CD4 expression during T-cell proliferation and differentiation, we identified a new differentiation pathway for the conversion of CD4+ T cells to DN regulatory T cells. We showed that the converted DN T cells retained a stable phenotype after restimulation and that furthermore, the disappearance of cell-surface CD4 molecules on converted DN T cells was a result of CD4 gene silencing. The converted DN T cells were resistant to activation-induced cell death (AICD) and expressed a unique set of cell-surface markers and gene profiles. These cells were highly potent in suppressing alloimmune responses both in vitro and in vivo in an antigen-specific manner. Perforin was highly expressed by the converted DN regulatory T cells and played a role in DN T-cell–mediated suppression. Our findings thus identify a new differentiation pathway for DN regulatory T cells and uncover a new intrinsic homeostatic mechanism that regulates the magnitude of immune responses. This pathway provides a novel, cell-based, therapeutic approach for preventing allograft rejection.

T cell Ig mucin (Tim) molecules modulate CD4⁺ T cell responses. In keeping with the view that Tim-1 generates a stimulatory signal for CD4⁺ T cell activation, we hypothesized that an agonist Tim-1–specific mAb would intensify the CD4⁺ T cell–dependant allograft response. Unexpectedly, we determined that a particular Tim-1–specific mAb exerted reciprocal effects upon the commitment of alloactivated T cells to regulatory and effector phenotypes. Commitment to the Th1 and Th17 phenotypes was fostered, whereas commitment to the Treg phenotype was hindered. Moreover, ligation of Tim-1 in vitro effectively deprogrammed Tregs and thus produced Tregs unable to control T cell responses. Overall, the effects of the agonist Tim-1–specific mAb on the allograft response stemmed from enhanced expansion and survival of T effector cells; a capacity to deprogram natural Tregs; and inhibition of the conversion of naive CD4⁺ T cells into Tregs. The reciprocal effects of agonist Tim-1–specific mAbs upon effector T cells and Tregs serve to prevent allogeneic transplant tolerance.

BACKGROUND AND PURPOSEEndostatin (ES) is a c‐terminal proteolytic fragment of collagen XVIII with promising antitumour properties in several tumour models, including human glioblastoma. We hypothesized that this peptide could interact with plasma membrane ion channels and modulate their functions.EXPERIMENTAL APPROACHUsing cell proliferation and migration assays, patch clamp and Western blot analysis, we studied the effects of ES on the proliferation and migration of human glioblastoma U87 cells, mediated by T‐type Ca²⁺channels.KEY RESULTSExtracellular application of ES reversibly inhibited T‐type Ca²⁺channel currents (T‐currents) in U87 cells, whereas L‐type Ca²⁺currents were not affected. This inhibitory effect was associated with a hyperpolarizing shift in the voltage‐dependence of inactivation but was independent of G‐protein and protein tyrosine kinase‐mediated pathways. All three α₁subunits of T‐type Ca²⁺channels (Ca_V3), α_1G(Ca_V3.1), α_1H(Ca_V3.2) and α_1I(Ca_V3.3), were endogenously expressed in U87 cells. Using transfected HEK293 or CHO cells, we showed that only Ca_V3.1 and Ca_V3.2, but not Ca_V3.3 or Ca_V1.2 (L‐type), channel currents were significantly inhibited. More interestingly, ES inhibited the proliferation and migration of U87 cells in a dose‐dependent manner. Pretreatment of the cells with the specific T‐type Ca²⁺channel blocker mibefradil occluded these inhibitory effects of ES.CONCLUSION AND IMPLICATIONSThis study provides the first evidence that the antitumour effects of ES on glioblastoma cells is through direct inhibition of T‐type Ca²⁺channels and gives new insights into the future development of a new class of antiglioblastoma agents that target the proliferation and migration of these cells.LINKED ARTICLEThis article is commented on by Santoniet al., pp. 1244–1246 of this issue. To view this commentary visithttp://dx.doi.org/10.1111/j.1476‐5381.2012.01908.x

Allergic asthma is an inflammatory disorder of the airway without satisfactory traditional therapies capable of controlling the underlying pathology. New approaches that can overcome the detrimental effects of immune dysregulation are thus desirable. Here we adoptively transfer ovalbumin (OVA) peptide-primed CD4⁻CD8⁻ double negative T (DNT) cells intravenously into a mouse model of OVA-induced allergic asthma to find that OVA-induced airway hyperresponsiveness, lung inflammation, mucus production and OVA-specific IgG/IgE production are significantly suppressed. The immunosuppressive function of the OVA-specific DNT cells is dependent on the inhibition of CD11b⁺ dendritic cell function, T follicular helper cell proliferation, and IL-21 production. Mechanistically, Lag3 contributes to MHC-II antigen recognition and trogocytosis, thereby modulating the antigen-specific immune regulation by DNT cells. The effectiveness of ex vivo-generated allergen-specific DNT cells in alleviating airway inflammation thus supports the potential utilization of DNT cell-based therapy for the treatment of allergic asthma.