Foxp3 + regulatory T cells in peripheral tissues (pT regs ) are instrumental in limiting inflammatory responses to non-self antigens. Within the intestine, pT regs are located primarily in the lamina propria, while intraepithelial CD4 + T cells (CD4 IELs ), which also exhibit anti-inflammatory properties and depend on similar environmental cues, reside in the epithelium. Using intravital microscopy, we show distinct cell dynamics of intestinal T regs and CD4 IELs . Upon migration to the epithelium, T regs lose Foxp3 and convert to CD4 IELs in a microbiota-dependent fashion, an effect attributed to the loss of the transcription factor ThPOK. Finally, we demonstrate that pT regs and CD4 IELs perform complementary roles in the regulation of intestinal inflammation. These results reveal intra-tissue specialization of anti-inflammatory T cells shaped by discrete niches of the intestine.The gut mucosa is exposed to large amounts of both harmless and potentially pathogenic stimuli on a daily basis, hence diverse immune regulatory mechanisms must operate to avoid inflammatory diseases (1). Peripheral Foxp3-expressing regulatory T cells (pT regs ) mediate suppression of a variety of immune cells and actively prevent inflammatory bowel diseases and food allergies (2-7). Similar to pT regs , Foxp3 − CD8αα + CD4 + intraepithelial lymphocytes (CD4 IELs ) depend on retinoic acid (RA) and transforming growth factor (TGF)-β signaling for their development and also have anti-inflammatory properties (4,(8)(9)(10)(11)(12)(13). However, while CD4 IELs accumulate in the intestinal epithelium, very few total T regs (including pT regs or thymically-derived T regs ) can be found at this site ( fig. S1A and B fig. S2A). Because previous studies have demonstrated that the majority of "ex-Foxp3" cells in the steady state were derived from uncommitted precursors that transiently upregulated Foxp3 (18), we also performed fate mapping after pulse-labeling iFoxp3 Tomato mice with tamoxifen (14), a strategy more likely to target bona fide T regs (19). Nevertheless, while stable Foxp3 expression was again observed in several peripheral tissues examined, over 50% of Tomato + CD4 + T cells that accumulated in the small intestine and almost 10% in the large intestine epithelium isolated from iFoxp3 Tomato mice no longer expressed Foxp3 fives weeks post tamoxifen administration ( fig. S2B and C). The contribution of Tomato + cells to the CD8αα + and CD8αβ + CD4 IEL pools was roughly 10% and 25%, respectively ( fig. S2D). Consistent with a ThPOK-dependent process, ex-T regs that underwent IEL differentiation showed low levels of ThPOK ( fig. S2E). These results indicate that a substantial proportion of intestinal T regs physiologically convert to CD4 IELs .Commensal bacteria play a major role in the induction of lamina propria pT regs in the large intestine (3,(5)(6)(7)20). In contrast, we observed an increased frequency of pT regs (Neuropilin-1 − Foxp3 + ) in the small intestinal epithelium isolated from germ-free (GF) mice when compared to...

Summary Enhancing repair of myelin is an important, but still elusive therapeutic goal in many neurological disorders1. In Multiple Sclerosis (MS), an inflammatory demyelinating disease, endogenous remyelination does occur but is frequently insufficient to restore function. Both parenchymal oligodendrocyte progenitor cells (OPCs) and endogenous adult neural stem cells (NSCs) resident within the subventricular zone (SVZ) are known sources of remyelinating cells2. Here, we characterize the contribution to remyelination of a subset of adult NSCs, identified by their expression of Gli1, a transcriptional effector of the Sonic Hedgehog (Shh) pathway. We show that these cells are recruited from the SVZ to populate demyelinated lesions in the forebrain but never enter healthy, white matter tracts. Unexpectedly, recruitment of this pool of NSCs, and their differentiation into oligodendrocytes, is significantly enhanced by genetic or pharmacological inhibition of Gli1. Importantly, complete inhibition of canonical hedgehog signaling was ineffective indicating that Gli1’s role in both augmenting hedgehog signaling and retarding myelination is specialized. Indeed, inhibition of Gli1 improves the functional outcome in a relapsing/remitting model of experimental autoimmune encephalomyelitis (RR-EAE) and is neuroprotective. Thus, endogenous NSCs can be mobilized for the repair of demyelinated lesions by inhibiting Gli1, identifying a new therapeutic avenue for the treatment of demyelinating disorders.

Transplanted individuals in operational tolerance (OT) maintain long-term stable graft function after completely stopping immunosuppression. Understanding the mechanisms involved in OT can provide valuable information about pathways to human transplantation tolerance. Here we report that operationally tolerant individuals display quantitative and functional preservation of the B-cell compartment in renal transplantation. OT exhibited normal numbers of circulating total B cells, naive, memory and regulatory B cells (Bregs) as well as preserved B-cell receptor repertoire, similar to healthy individuals. In addition, OT also displayed conserved capacity to activate the cluster of differentiation 40 (CD40)/signal transducer and activator of transcription 3 (STAT3) signaling pathway in Bregs, in contrast, with chronic rejection. Rather than expansion or higher activation, we show that the preservation of the B-cell compartment favors OT.

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Strategies to minimize the immunogenicity and toxicity of murine anti-CD3 antibodies (e.g. OKT3) are of special interest for organ transplantation and for the treatment of autoimmune diseases. In the present work, we have developed two humanized anti-CD3 antibodies. These molecules were shown to bind to human CD3, though less efficiently, and display less mitogenic activity than OKT3. These results prompted us to investigate whether this reduced mitogenic potential was associated with the development of anti-inflammatory properties. Indeed, in peripheral blood mononuclear cells (PBMCs), the humanized antibody versions induced a predominantly anti-inflammatory cytokine profile, in contrast with the pro-inflammatory profile induced by OKT3. Neither OKT3 nor the humanized versions induced the expression of IL-4, IL-2 or TGF-beta. Both humanized antibodies induced significantly lower production of IFN-gamma and IL-5 and slightly higher production of IL-10 than OKT3. This immunomodulatory profile was most evident by the 80-fold higher ratio of IL-10/IFN-gamma production in PBMCs cultured in the presence of the humanized antibodies, compared to those stimulated with OKT3. Furthermore, these humanized anti-CD3 antibodies induced a late FOXP3 gene expression while OKT3 led to a more transient expression of FOXP3. Taken our results, we suggest that these humanized anti-CD3 antibodies may promote the development of T cells with immunoregulatory activity.