IL-6 Inhibits Upregulation of Membrane-Bound TGF-ß 1 on CD4+ T Cells and Blocking IL-6 Enhances Oral Tolerance.

Oral administration of Ag induces regulatory T cells that express latent membrane-bound TGF-ß (latency-associated peptide [LAP]) and have been shown to play an important role in the induction of oral tolerance. We developed an in vitro model to study modulation of LAP+ on CD4+ T cells. The combination of anti-CD3 mAb, anti-CD28 mAb, and recombinant IL-2 induced expression of LAP on naive CD4+ T cells, independent of Foxp3 or exogenous TGF-ß. In vitro generated CD4+LAP+Foxp3- T cells were suppressive in vitro, inhibiting proliferation of naive CD4+ T cells and IL-17A secretion by Th17 cells. Assessing the impact of different cytokines and neutralizing Abs against cytokines, we found that LAP induction was decreased in the presence of IL-6 and IL-21, and to a lesser extent by IL-4 and TNF-α. IL-6 abrogated the in vitro induction of CD4+LAP+ T cells by STAT3-dependent inhibition of Lrrc32 (glycoprotein A repetitions predominant [GARP]), the adapter protein that tethers TGF-ß to the membrane. Oral tolerance induction was enhanced in mice lacking expression of IL-6R by CD4+ T cells and by treatment of wild-type mice with neutralizing anti-IL-6 mAb. These results suggest that proinflammatory cytokines interfere with oral tolerance induction and that blocking the IL-6 pathway is a potential strategy for enhancing oral tolerance in the setting of autoimmune and inflammatory diseases.

High frequency of fetal cells within a primitive stem cell population in maternal blood.

BACKGROUND: During pregnancy, fetal cells enter the maternal bloodstream resulting in fetal cell microchimerism. The fetal cells persist in the mother for decades and colonize a variety of maternal organs. They are associated with maternal autoimmune diseases and may also participate in tissue repair. The identity of the microchimeric cells is not certain but they must be able to persist long-term and have potential for multitissue differentiation. METHODS AND RESULTS: Here we tested the hypothesis that the fetal microchimeric cells are primitive stem cells, represented by CD34+ adherent cells, which have a wide potential for differentiation. We isolated these stem cells from the blood of pregnant females (n = 25) and detected fetal cells of the correct gender, using fluorescence in situ hybridization, in a high proportion (71% male fetuses and 90% female fetuses; false positive rate 11%, false negative rate 29%) of cases. By RT-PCR, we demonstrated that the cells express Oct-4, Nanog and Rex-1. No fetal cells were detected in the mononuclear or total CD34+ cell populations but high frequencies (mean 11.8%) of fetal cells were detected in the adherent CD34+ cell population. CONCLUSIONS: These results identify adherent CD34+ stem cells as candidate fetal microchimeric cells, which are capable of sustaining the fetal cell population in the long term and have the ability to colonize multiple tissues and organs.

Identification and characterization of latency-associated peptide-expressing γδ T cells.

γδ T cells are a subset of lymphocytes specialized in protecting the host against pathogens and tumours. Here we describe a subset of regulatory γδ T cells that express the latency-associated peptide (LAP), a membrane-bound TGF-ß1. Thymic CD27+IFN-γ+CCR9+α4ß7+TCRγδ+ cells migrate to the periphery, particularly to Peyer's patches and small intestine lamina propria, where they upregulate LAP, downregulate IFN-γ via ATF-3 expression and acquire a regulatory phenotype. TCRγδ+LAP+ cells express antigen presentation molecules and function as antigen presenting cells that induce CD4+Foxp3+ regulatory T cells, although TCRγδ+LAP+ cells do not themselves express Foxp3. Identification of TCRγδ+LAP+ regulatory cells provides an avenue for understanding immune regulation and biologic processes linked to intestinal function and disease.

Characterization and clinical application of human CD34+ stem/progenitor cell populations mobilized into the blood by granulocyte colony-stimulating factor.

A phase I study was performed to determine the safety and tolerability of injecting autologous CD34(+) cells into five patients with liver insufficiency. The study was based on the hypothesis that the CD34(+) cell population in granulocyte colony-stimulating factor (G-CSF)-mobilized blood contains a subpopulation of cells with the potential for regenerating damaged tissue. We separated a candidate CD34(+) stem cell population from the majority of the CD34(+) cells (99%) by adherence to tissue culture plastic. The adherent and nonadherent CD34(+) cells were distinct in morphology, immunophenotype, and gene expression profile. Reverse transcription-polymerase chain reaction-based gene expression analysis indicated that the adherent CD34(+) cells had the potential to express determinants consistent with liver, pancreas, heart, muscle, and nerve cell differentiation as well as hematopoiesis. Overall, the characteristics of the adherent CD34(+) cells identify them as a separate putative stem/progenitor cell population. In culture, they produced a population of cells exhibiting diverse morphologies and expressing genes corresponding to multiple tissue types. Encouraged by this evidence that the CD34(+) cell population contains cells with the potential to form hepatocyte-like cells, we gave G-CSF to five patients with liver insufficiency to mobilize their stem cells for collection by leukapheresis. Between 1 x 10(6) and 2 x 10(8) CD34(+) cells were injected into the portal vein (three patients) or hepatic artery (two patients). No complications or specific side effects related to the procedure were observed. Three of the five patients showed improvement in serum bilirubin and four of five in serum albumin. These observations warrant further clinical trials.