Regulatory T (T reg) cells are critical regulators of immune tolerance. Most T reg cells are defined based on expression of CD4, CD25, and the transcription factor, FoxP3. However, these markers have proven problematic for uniquely defining this specialized T cell subset in humans. We found that the IL-7 receptor (CD127) is down-regulated on a subset of CD4+ T cells in peripheral blood. We demonstrate that the majority of these cells are FoxP3+, including those that express low levels or no CD25. A combination of CD4, CD25, and CD127 resulted in a highly purified population of T reg cells accounting for significantly more cells that previously identified based on other cell surface markers. These cells were highly suppressive in functional suppressor assays. In fact, cells separated based solely on CD4 and CD127 expression were anergic and, although representing at least three times the number of cells (including both CD25+CD4+ and CD25−CD4+ T cell subsets), were as suppressive as the “classic” CD4+CD25hi T reg cell subset. Finally, we show that CD127 can be used to quantitate T reg cell subsets in individuals with type 1 diabetes supporting the use of CD127 as a biomarker for human T reg cells.

Abnormalities in CD4+CD25+Foxp3+ regulatory T (T reg) cells have been implicated in susceptibility to allergic, autoimmune, and immunoinflammatory conditions. However, phenotypic and functional assessment of human T reg cells has been hampered by difficulty in distinguishing between CD25-expressing activated and regulatory T cells. Here, we show that expression of CD127, the α chain of the interleukin-7 receptor, allows an unambiguous flow cytometry–based distinction to be made between CD127lo T reg cells and CD127hi conventional T cells within the CD25+CD45RO+RA− effector/memory and CD45RA+RO− naive compartments in peripheral blood and lymph node. In healthy volunteers, peripheral blood CD25+CD127lo cells comprised 6.35 ± 0.26% of CD4+ T cells, of which 2.05 ± 0.14% expressed the naive subset marker CD45RA. Expression of FoxP3 protein and the CD127lo phenotype were highly correlated within the CD4+CD25+ population. Moreover, both effector/memory and naive CD25+CD127lo cells manifested suppressive activity in vitro, whereas CD25+CD127hi cells did not. Cell surface expression of CD127 therefore allows accurate estimation of T reg cell numbers and isolation of pure populations for in vitro studies and should contribute to our understanding of regulatory abnormalities in immunopathic diseases.

Type 2 immunity is critical for defense against cutaneous infections, but also underlies the development of allergic skin diseases. We report the identification in normal murine dermis of an abundant, phenotypically unique group 2 innate lymphoid cell (ILC2) subset that depends on interleukin 7 (IL-7) and constitutively produces IL-13. Intravital multiphoton microscopy revealed that dermal ILC2 specifically interact with mast cells, whose function was suppressed by IL-13. Treatment of Rag1−/− mice with IL-2 resulted in the expansion of activated, IL-5-producing dermal ILC2, leading to spontaneous dermatitis characterized by eosinophil infiltrate and activated mast cells. Our data show that ILC2 exhibit both pro- and anti-inflammatory properties and uncover a novel interactive pathway between two innate immune cell populations implicated in type 2 immunity and allergic diseases.

SummaryTo study the factors that determine whether CD4 + T cells produce interleukin 4 (II.-4) or interferon 3' (IFN-3') upon stimulation we used a system allowing naive T cells to be primed in vitro by spedfic antigen. Dense CD4 + T cells were purified from mice that expressed transgenes encoding a T cell receptor specific for pigeon cytochrome C peptide 88-104 in association with I-E k. These T cells produced very limited amounts of Ib4 and IFN-3' upon immediate challenge with 88-104 and antigen-presenting cells (APC). However, after an initial "priming" culture in which they were incubated for 4 d in the presence of 88-104, APC, and 1,000 U/m1 IL-4, the T ceUs acquired the capacity to produce substantial amounts of IL-4 upon rechallenge but made very little IFN-3'. Cells primed in the absence of ID4 produced IFN-3' upon rechallenge but virtually no II.-4. The inhibitory effect of II.-4 on IFN-3' production did no appear to be mediated by the induction of Ibl0 production since IL-10 addition to initial cultures did not suppress priming for IFN-3" production, nor did anti-IL-10 block the inhibitory effect of II.-4. IFN-3' itself did not increase priming for IFN-3' production, nor did anti-IFN-3` reduce such priming. IFN-3` did, however, diminish priming for II.-4 production when limiting amounts of Ib4 (100 U/ml) were used in the initial culture. The dominant effect of Ib4 in determining the lymphokine-producing phenotype of primed cells was observed with dendritic cells (DC), activated B cells, and I-Ek-transfected fibroblasts as APC. However, the different APC did vary in their potency, with DC being superior to activated B cells, which were superior to transfected fibroblasts.

The mammalian immune system has an extraordinary potential for making receptors that sense and neutralize any chemical entity entering the body. Inevitably, some of these receptors recognize components of our own body, and so cellular mechanisms have evolved to control the activity of these 'forbidden' receptors and achieve immunological self tolerance. Many of the genes and proteins involved are conserved between humans and other mammals. This provides the bridge between clinical studies and mechanisms defined in experimental animals to understand how sets of gene products coordinate self-tolerance mechanisms and how defects in these controls lead to autoimmune disease. . A significant fraction of the receptors generated by both these processes bind to one or more self components in the body -a byproduct of a deliberately random receptor-generating process. Between 20 and 50% of TCRs and BCRs generated by V(D)J recombiNature Publishing Group

Preeclampsia is the leading cause of morbidity and mortality in pregnancy. Although the etiology of preeclampsia is still unclear, it is believed to involve rejection of the fetus, possibly due to an imbalance between regulatory (Treg) and effector T cells. To test this, we compared the frequencies of circulating CD4+ T cells expressing Foxp3, IFN-γ, IL-10, or IL-17 at the end of the third trimester of healthy and preeclamptic pregnancies. The size of the Treg cell compartment, defined by the frequency of CD4+CD25high, CD4+CD127lowCD25+, and CD4+Foxp3+ cells was significantly higher in normal compared with preeclamptic pregnancies. CD4+CD25high and CD4+CD127lowCD25+ populations in preeclampsia were not significantly different from those in nonpregnant controls, whereas CD4+Foxp3+ cells numbersre slightly lower in preeclampsia. The suppressive activity of ex vivo-sorted CD4+CD127lowCD25+ Treg cells was not significantly different between the three study groups. The percentage of CD4+IL-17-producing T cells decreased significantly in healthy compared with preeclamptic pregnancies and nonpregnant controls, whereas CD4+IL-10- and CD4+IFN-γ-producing cells remained unchanged. Consequently, the ratio of Foxp3+ Treg to IL-17-expressing CD4+ T cells was significantly increased in healthy but not in preeclamptic pregnancies. Thus, preeclampsia is associated with the absence of normal systemic skewing away from IL-17 production toward Foxp3+ expression. Finally, preeclamptic women had significantly higher levels of soluble endoglin, an inhibitor of TGF-β receptor signaling, which may bias toward IL-17 production. These results suggest that homeostasis between regulatory and proinflammatory CD4+ T cells might be pivotal for the semiallogeneic fetus to be tolerated within the maternal environment.

To test models of T-cell recognition, mice transgenic for T-cell receptor alpha or beta chain have been immunized with variant peptides that force changes in the resulting T-cell response. In particular, charge substitutions on the peptide often elicit reciprocal charges in the junctional (CDR3) sequences of T-cell receptor V alpha or V beta chains, indicating direct T-cell receptor-peptide contact, and allowing derivation of a topology for the T-cell receptor-MHC interaction. At one position on the peptide, variants transformed a homogeneous V beta response into a very heterogeneous one.

The dermis contains a novel population of γδT cells that are distinct from epidermal γδT cells and produce IL-17 in response to mycobacterial infection.