A link between PDL1 and T regulatory cells in fetomaternal tolerance

Acceptance of the fetus expressing allogeneic paternal Ags by the mother is a physiologic model of transplantation tolerance. Various mechanisms contribute to fetal evasion from immune attack by maternal leukocytes. We have recently demonstrated that the inhibitory costimulatory molecule PDL1 plays a critical role in fetomaternal tolerance in that PDL1 blockade or deficiency resulted in decreased allogeneic fetal survival rates. CD4(+)CD25(+) T regulatory cells (Tregs) have also been demonstrated to play an important role in fetomaternal tolerance. Since PDL1 is expressed on Tregs, we explored the interactions between PDL1 and Tregs in vivo in a mouse model of fetomaternal tolerance. Depletion of CD25(+) T cells abrogated the effect of anti-PDL1 Ab indicating that the effect of PDL1 is possibly mediated by CD25(+) Tregs. Adoptive transfer of Tregs from wild-type but not PDL1-deficient mice into PDL1-deficient recipients significantly improved fetal survival. The frequency, phenotype and placental trafficking of Tregs from PDL1-deficient mice were similar to those of wild-type controls, but were defective in inhibiting alloreactive Th1 cells in vitro. This is the first report providing evidence for a link between PDL1 and T regulatory cells in mediating fetomaternal tolerance.     

The link between the PDL1 costimulatory pathway and Th17 in fetomaternal tolerance

Fetomaternal tolerance has been shown to depend both on regulatory T cells (Tregs) and negative signals from the PD1-PDL1 costimulatory pathway. More recently, IL-17-producing T cells (Th17) have been recognized as a barrier in inducing tolerance in transplantation. In this study, we investigate the mechanisms of PDL1-mediated regulation of fetomaternal tolerance using an alloantigen-specific CD4(+) TCR transgenic mouse model system (ABM-tg mouse). PDL1 blockade led to an increase in embryo resorption and a reduction in litter size. This was associated with a decrease in Tregs, leading to a lower Treg/effector T cell ratio. Moreover, PDL1 blockade inhibited Ag-specific alloreactive T cell apoptosis and induced apoptosis of Tregs and a shift toward higher frequency of Th17 cells, breaking fetomaternal tolerance. These Th17 cells arose predominantly from CD4(+)Foxp3(-) cells, rather than from conversion of Tregs. Locally in the placenta, similar decrease in regulatory and apoptotic markers was observed by real-time PCR. Neutralization of IL-17 abrogated the anti-PDL1 effect on fetal survival rate and restored Treg numbers. Finally, the adoptive transfer of Tregs was also able to improve fetal survival in the setting of PDL1 blockade. This is to our knowledge the first report using an alloantigen-specific model that establishes a link between PDL1, Th17 cells, and fetomaternal tolerance.     

Sphingolipid Pathway Regulates Innate Immune Responses at the Fetomaternal Interface during Pregnancy

For a successful pregnancy, the mother''s immune system has to tolerate the semiallogeneic fetus. A deleterious immune attack is avoided by orchestration of cellular, hormonal, and enzymatic factors. However, the precise mechanisms underlying fetomaternal tolerance are not yet completely understood. In this study, we demonstrate that sphingolipid metabolism constitutes a novel signaling pathway that is indispensable for fetomaternal tolerance by regulating innate immune responses at the fetomaternal interface. Perturbation of the sphingolipid pathway by disruption of the sphingosine kinase gene (Sphk) during pregnancy caused unusually high expression of neutrophil chemoattractants, CXCL1 and CXCL2, in the decidua, leading to a massive infiltration of neutrophils into the fetomaternal interface with enhanced oxidative damage, resulting in early fetal death. Sphk-deficient mice also exhibited neutrophilia in the peripheral blood, enhanced generation of granulocytes in the bone marrow, and a decrease in the number of decidual natural killer cells. The blockage of neutrophil influx protected Sphk-deficient mice against pregnancy loss. Notably, a similar result was obtained in human decidual cells, in which Sphk deficiency dramatically increased the secretion of CXCL1 and IL-8. In conclusion, our findings suggest that the sphingolipid metabolic pathway plays a critical role in fetomaternal tolerance by regulating innate immunity at the fetomaternal interface both in mice and humans, and it could provide novel insight into the development of therapeutic strategies to treat idiopathic pregnancy loss in humans.     

Cyclosporin a improves pregnancy outcome by promoting functions of trophoblasts and inducing maternal tolerance to the allogeneic fetus in abortion-prone matings in the mouse

The embryo expresses paternal antigens foreign to the mother, and therefore has been viewed as a natural allograft. Cyclosporin A (CsA) is an immunosuppressant for preventing allograft rejection. Little is known, however, about the modulating effect of CsA on the materno-fetal relationship. In this study, pregnant CBA/J female mice mated with DBA/2 or BALB/c male mice as abortion-prone and normal pregnancy matings were administered, respectively, with CsA at Day 4 of gestation. We demonstrated that the administration of CsA at the window of implantation resulted in maternal T-cell tolerance to paternal antigen, and it improved pregnancy outcome in the CBA/J multiply sign in box DBA/2 abortion-prone matings. CsA administration enhanced Th2 and reduced Th1 cytokine production at the materno-fetal interface, and it expanded peripheral CD4(+)CD25(+) FOXP3(+) regulatory T cells in abortion-prone matings, implying development of Th2 bias and regulatory T cells. On the other hand, we observed that treatment with CsA led to enhanced growth and invasiveness of trophoblasts in the abortion-prone matings. Together, these findings indicate that CsA in lower dosages can induce materno-fetal tolerance and improve the biologic functions of trophoblast cells in the abortion-prone matings, leading to a successful pregnancy, which is useful in clinical therapeutics for spontaneous pregnancy wastage and other pregnancy complications.     

Effect of interleukin-10 null mutation on maternal immune response and reproductive outcome in mice

Interleukin-10 (IL-10) is an anti-inflammatory and immune-deviating cytokine expressed in the endometrium and placenta. IL-10 null mutant (IL-10-/-) mice have been employed to examine the role of IL-10 in regulating immune events in early pregnancy and its significance in implantation and pregnancy success. The inflammatory response elicited in endometrial tissue by insemination was amplified in IL-10-/- mice, with a 66% increase in leukocytes in the endometrial stroma on Day 3 of pregnancy. Despite this, no evidence of abnormal type 1/type 2 skewing was seen in T-lymphocytes from lymph nodes draining the uterus. On Day 18 of gestation, IL-10-/- females mated with IL-10-/- males had 15% more implantation sites and 27% more viable fetuses than pregnant wild-type (IL-10+/+) mice. Placental weight was unaffected, but fetal weight and the fetal:placental weight ratio were higher in IL-10-/- pregnancies. Similar data were obtained in allogeneic pregnancies when IL-10-/- females were mated with major-histocompatibility complex (MHC) disparate IL-10-/- males. Pups delivered by IL-10-/- mothers had increased birth weight and followed an altered growth trajectory, with growth impairment evident from early postnatal life into adulthood, which was reflected in alterations in body composition at 14 wk of age. This study shows that although IL-10 is not essential for maternal immune tolerance or successful pregnancy irrespective of MHC disparity in the fetus, maternal IL-10 is a determinant of growth trajectory in progeny in utero and after birth.     

Galectin-8 Ameliorates Murine Autoimmune Ocular Pathology and Promotes a Regulatory T Cell Response

Galectins have emerged as potent immunoregulatory agents that control chronic inflammation through distinct mechanisms. Here, we report that treatment with Galectin-8 (Gal-8), a tandem-repeat member of the galectin family, reduces retinal pathology and prevents photoreceptor cell damage in a murine model of experimental autoimmune uveitis. Gal-8 treatment increased the number of regulatory T cells (Treg) in both the draining lymph node (dLN) and the inflamed retina. Moreover, a greater percentage of Treg cells in the dLN and retina of Gal-8 treated animals expressed the inhibitory coreceptor cytotoxic T lymphocyte antigen (CTLA)-4, the immunosuppressive cytokine IL-10, and the tissue-homing integrin CD103. Treg cells in the retina of Gal-8-treated mice were primarily inducible Treg cells that lack the expression of neuropilin-1. In addition, Gal-8 treatment blunted production of inflammatory cytokines by retinal T helper type (T_H) 1 and T_H17 cells. The effect of Gal-8 on T cell differentiation and/or function was specific for tissues undergoing an active immune response, as Gal-8 treatment had no effect on T cell populations in the spleen. Given the need for rational therapies for managing human uveitis, Gal-8 emerges as an attractive therapeutic candidate not only for treating retinal autoimmune diseases, but also for other T_H1- and T_H17-mediated inflammatory disorders.     

Mesenchymal stem cells alter the frequency and cytokine profile of natural killer cells in abortion-prone mice

Natural killer cells, which play a pivotal role in the establishment and maintenance of normal pregnancy, are the most abundant leukocytes at the fetomaternal interface that their subsets frequencies and cytokine profile are influential factors in the preservation of the decidual tolerogenic microenvironment. Any imbalance in NK cells' frequency and functions could be associated with pregnancy failure. Mesenchymal stem cells (MSCs) are shown to have immunomodulatory effects on NK cells and their cytokine profile. The purpose of this study is to evaluate the impact of MSCs therapy on the cytokine profiles and subpopulations of NK cells in a murine model of recurrent pregnancy loss. Adipose-derived MSCs were injected intraperitoneally to the abortion-prone mice on Day 4.5 of gestation. The abortion rate was determined after MSCs administration and the frequency and cytokine profiles of the different subsets of NK cells were determined using the flow cytometry. Our results showed that, in abortion-prone mice, the frequency of CD49b⁺ NK cells was significantly higher than normal pregnant mice that decreased after therapy. We also demonstrated that MSCs downregulated the production of IFN-γ and upregulated IL-4 and IL-10 production by uNK cells. These findings indicate that MSCs can decrease the infiltration of CD49b⁺ NK cells to the fetomaternal interface and modulate the cytokine profile of NK cells from inflammatory to tolerogenic profile and thereby improve the tolerogenic microenvironment at the fetomaternal interface in benefit of pregnancy maintenance.     

Loss of the surface antigen 3G11 characterizes a distinct population of anergic/regulatory T cells in experimental autoimmune encephalomyelitis

T cell anergy is an important mechanism in the induction of peripheral tolerance against autoimmune diseases, yet no surface marker unique to anergic T cells in these diseases has been identified. In this study we induced in vivo anergy by i.v. tolerance against experimental autoimmune encephalomyelitis in myelin basic protein TCR transgenic mice, and showed that the hyporesponsiveness of autoantigen-reactive T cells from tolerized mice was associated with a dramatic loss of 3G11, a cell surface molecule on the surface of CD4+ T cells. Purified 3G11-CD4+ T cells lost autoantigen-induced proliferation and IL-2 production, whereas 3G11+CD4+ T cells retained responsiveness. Furthermore, 3G11- T cells actively suppressed proliferation and Th1 cytokine production of 3G11+ T cells and splenocytes of nontolerized mice. Active suppression by 3G11- T cells was at least partially due to soluble immunoregulatory factors, including IL-10. The T regulatory property of 3G11- T cells was confirmed in vivo because the transfer of purified 3G11- T cells effectively suppressed clinical experimental autoimmune encephalomyelitis. We conclude that loss of the surface molecule 3G11 characterizes a distinct population of anergic/regulatory T cells. This is the first demonstration of the ability to identify and purify anergic T cells by a distinct cell surface marker in an autoimmune disease and paves the way for a better understanding of the mechanism of tolerance in autoimmune diseases.     

Intercellular adhesion molecule-1/LFA-1 cross talk is a proximate mediator capable of disrupting immune integration and tolerance mechanism at the feto-maternal interface in murine pregnancies

Our understanding why a woman's immune system does not reject her histoincompatible fetus is still very limited. Distinct insights into the mechanisms involved in pregnancy maintenance may help us to prevent pregnancy complications, e.g., miscarriages or pre-eclampsia. Immune integration and tolerance at the feto-maternal interface appear to be indispensable for successful pregnancy maintenance. Little is known about the cross talk between ICAM-1, expressed on epithelium, endothelium, and APC, and its ligand, LFA-1, at the feto-maternal interface. However, based on the role of ICAM-1/LFA-1 in allograft acceptance or rejection upon transplantation, adhesion molecules are likely to interfere with successful pregnancy outcome. In this study, we tested the hypothesis that ICAM-1/LFA-1 pathways may be involved in pregnancy rejection in murine models. By blocking ICAM-1/LFA-1-mediated intercellular adhesion events, we show that fetal immune acceptance is restored in challenged pregnancies (e.g., upon exposure to sound stress), and adoptive transfer of LFA-1 cells into pregnant mice induces rejection only in abortion-prone mouse models. ICAM-1/LFA-1 cross talk leads to increased recruitment of proinflammatory cells to the implantation site, promotes dendritic cell maturation in the decidua, and subsequently induces additional local Th1 polarization via mature dendritic cells. Furthermore, our observations clearly point out that mechanisms of fetal tolerance, e.g., indoleamine 2,3-dioxygenase expression, presence of CD4+CD25bright regulatory T cells, and synthesis of asymmetric Abs, are ICAM-1/LFA-1 dependent. Hence, our data shed light on a hierarchical network of immune integration at the feto-maternal interface, in which ICAM-1/LFA-1 cross talk is clearly a proximate mediator capable of disrupting successful pregnancy maintenance.     

Immune tolerance to combined organ and bone marrow transplants after fractionated lymphoid irradiation involves regulatory NK T cells and clonal deletion

Immune tolerance to organ transplants has been reported in laboratory animals and in humans after nonmyeloablative conditioning of the host and infusion of donor bone marrow cells. We examined the mechanisms of immune tolerance to mouse cardiac allografts in MHC-mismatched hosts that developed mixed chimerism after posttransplant conditioning with a 2-wk course of multiple doses of lymphoid tissue irradiation, depletive anti-T cell Abs, and an infusion of donor bone marrow cells. When CD1(-/-) or J(alpha)281(-/-) hosts with markedly reduced NK T cells were used instead of wild-type hosts, then the conditioning regimen failed to induce tolerance to the heart allografts despite the development of mixed chimerism. Tolerance could be restored to the CD1(-/-) hosts by infusing enriched T cells from the bone marrow of wild-type mice containing CD1-reactive T cells but not from CD1(-/-) host-type mice. Tolerance could not be induced in either IL-4(-/-) or IL-10(-/-) hosts given the regimen despite the development of chimerism and clonal deletion of host T cells to donor MHC-Ags in the IL-10(-/-) hosts. We conclude that immune tolerance to bone marrow transplants involves clonal deletion, and tolerance to heart allografts in this model also involves regulatory CD1-reactive NK T cells.     

Pregnancy allows the transfer and differentiation of fetal lymphoid progenitors into functional T and B cells in mothers

T lymphocytes of fetal origin found in maternal circulation after gestation have been reported as a possible cause for autoimmune diseases. During gestation, mothers acquire CD34+CD38+ cells of fetal origin that persist decades. In this study, we asked whether fetal T and B cells could develop from these progenitors in the maternal thymus and bone marrow during and after gestation. RAG-/--deficient female mice (Ly5.2) were mated to congenic wild-type Ly5.1 mice (RAG+/+). Fetal double-positive T cells (CD4+CD8+) with characteristic TCR and IL-7R expression patterns could be recovered in maternal thymus during the resulting pregnancies. We made similar observations in the thymus of immunocompetent mothers. Such phenomenon was observed overall in 12 of 68 tested mice compared with 0 of 51 controls (p=0.001). T cells could also be found in maternal spleen and produced IFN-gamma in the presence of an allogenic or an Ag-specific stimulus. Similarly, CD19+IgM+ fetal B cells as well as plasma Igs could be found in maternal RAG-/- bone marrow and spleen after similar matings. Our results suggest that during gestation mothers acquire fetal lymphoid progenitors that develop into functional T cells. This fetal cell microchimerism may have a direct impact on maternal health.     

The ICOS molecule plays a crucial role in the development of mucosal tolerance

The ICOS molecule stimulates production of the immunoregulatory cytokine IL-10, suggesting an important role for ICOS in controlling IL-10-producing regulatory T cells and peripheral T cell tolerance. In this study we investigate whether ICOS is required for development of oral, nasal, and high dose i.v. tolerance. Oral administration of encephalitogenic myelin oligodendrocyte glycoprotein (MOG) 35-55 peptide to ICOS-deficient (ICOS-/-) mice did not inhibit experimental autoimmune encephalomyelitis (EAE), T cell proliferation, or IFN-gamma production, in striking contrast to wild-type mice. Similarly, intranasal administration of MOG(35-55) before EAE induction suppressed EAE and T cell responses in wild-type, but not in ICOS-/-, mice. In contrast, ICOS-/- mice were as susceptible as wild-type mice to high dose tolerance. These results indicate that ICOS plays an essential and specific role in mucosal tolerance and that distinct costimulatory pathways differentially regulate different forms of peripheral tolerance. Surprisingly, CD4+ cells from MOG-fed wild-type and ICOS-/- mice could transfer suppression to wild-type recipients, indicating that functional regulatory CD4+ cells can develop in the absence of ICOS. However, CD4+ T cells from MOG-fed wild-type mice could not transfer suppression to ICOS-/- recipients, suggesting that ICOS may have a key role in controlling the effector functions of regulatory T cells. These results suggest that stimulating ICOS may provide an effective therapeutic approach for promoting mucosal tolerance.     

Uterine NK cells mediate inflammation-induced fetal demise in IL-10-null mice

Specialized NK cells are recruited in high numbers to the mammalian embryo implantation sites, yet remain pregnancy compatible. It is not well understood whether uterine NK (uNK) cells become adversely activated and mediate fetal demise, a common complication of early pregnancy. In this study we show that mating of IL-10(-/-) mice resulted in fetal resorption or intrauterine growth restriction in response to very low doses of LPS. Pregnancy in congenic wild-type mice was normal even at 10-fold higher LPS doses. Fetal resorption in IL-10(-/-) mice was associated with a significant increase in uNK cell cytotoxic activation and invasion into the placenta. Depletion of uNK cells, TNF-alpha neutralization, or IL-10 administration rescued pregnancy in LPS-treated IL-10(-/-) animals. Our results identify an immune mechanism of fetal demise involving IL-10 deficiency, NK cells, and inflammation. These results may provide insight into adverse pregnancy outcomes in humans.     

Cutting edge: trans-signaling via the soluble IL-6R abrogates the induction of FoxP3 in naive CD4+CD25 T cells

Chronic inflammatory diseases may develop when regulatory T cells (Tregs) fail to control the balance between tolerance and immunity. Alternatively, activated immune cells might prevent the induction or activation of Tregs in such diseases. In this study, we demonstrate that trans-signaling into T cells via the soluble IL-6 receptor completely abrogates the de novo induction of adaptive Tregs. Mechanistically, IL-6 trans-signaling augmented the expression of the TGF-beta signaling inhibitor SMAD7. Consequently, SMAD7 overexpression in T cells using newly created transgenic mice rendered CD4(+)CD25(-) T cells resistant to the induction of FoxP3. Finally, IL-6 trans-signaling inhibited Treg-mediated suppression in a murine model of colitis. In summary, IL-6 trans-signaling into T cells emerges as a key pathway for blockade of the development of adaptive Tregs and thus may play a pivotal role in shifting the balance between effector and regulatory T cell numbers in chronic inflammatory and autoimmune diseases.     

Regulation of type 1 diabetes by a self-MHC class II peptide: role of transforming growth factor beta (TGF-beta).

The present study was undertaken to analyze the regulatory T cells generated in response to class I derived self-I-A beta(g7) (54-76) peptide. It was observed T cells from young unprimed type 1 diabetes (T1D) prone NOD mice did not respond to self-I-A beta(g7) (54-76) peptide although T cells from primed young NOD mice showed a strong response. T cells from young unprimed BALB/c mice responded to self-I-A beta(d) (62-78) peptide. However, a breakdown of tolerance to these peptides was observed with age in both the strains. Culture supernatant from I-A beta(g7) (54-76) peptide-primed cells secreted large amounts of TGF-beta and inhibited T cell responses in allogeneic-MLR. Further, I-A beta(g7) (54-76) peptide specific T cell lines from young (I-A.Y) and diabetic (I-A.D) NOD mice were established. I-A.Y secreted IL-4, TGF-beta and IL-10 while I-A.D T cell line secreted IL-10 and IFN-gamma. We found that I-A.D T cell line induced diabetes when transferred in NOD/SCID mice but I-A.Y T cell line did not induce disease. These results show that immunization of NOD mice with I-A beta(g7) (54-76) peptide at a younger age induces a regulatory T cell response suggesting that correcting the defects in immunoregulatory mechanisms using self-MHC peptides may be one of the approaches to prevent autoimmune diseases like T1D.     

Mechanisms of peripheral tolerance following intracameral inoculation are independent of IL-13 or STAT6

The peripheral tolerance that is elicited by the anterior chamber-associated immune deviation (ACAID) protocol is characterized by impairment of Th1 responses such as delayed-type hypersensitivity. It has been proposed that suppression of Th1 responses is mediated by a deviation toward Th2 responses. Because NKT cells have a prominent role in ACAID and NKT cell-derived IL-13 is required in a tumor model of tolerance, we postulated that NKT cell-derived Th2 cytokines might have a role in ACAID. However, contrary to the tumor model, in this study we show that NKT cells from IL-13-deficient mice or IL-4/IL-13 double deficient mice were able to reconstitute the capability of J alpha18-deficient mice (lacking invariant NKT) to develop peripheral tolerance postintracameral inoculation of Ag. Also, we were able to induce peripheral tolerance directly in IL-13-deficient, IL-4/IL-13-double deficient, and STAT6-deficient mice by inoculation of Ag into their eye. We conclude that neither IL-4 nor IL-13 cytokines are required for the generation of efferent CD8+ T regulatory cells during eye-induced peripheral tolerance. We propose that Ags inoculated into the anterior chamber of the eye induce the immunoresponse to deviate from producing immune T effector cells to producing efferent T regulatory cells, rather than deviating from Th1- to Th2-type effector cells.     

B7H1-Ig fusion protein activates the CD4+ IFN-gamma receptor+ type 1 T regulatory subset through IFN-gamma-secreting Th1 cells

It has been demonstrated in our previous work that, in the human skin-grafting model, the expression of costimulatory molecule B7H1 (PD-L1) by keratinocytes plays an essential role in inducing local tolerance via activation of IL-10-secreting T cells. This study further analyzes the role of B7H1 in differentiation of type 1 T regulatory (Tr1) cells and explores underlying mechanisms. Mouse fusion protein B7H1-Ig is used, together with immobilized anti-CD3 mAb, to costimulate the purified naive CD4+ T cells. B7H1-Ig-treated CD4+ T cells were found to activate a characteristic Tr1 population possessing a CD4+ CD25- Foxp3- CD45RBlow phenotype. These regulatory T cells strongly inhibited the Th1-dominated MLR by secretion of IL-10 and TGF-beta. Moreover, B7H1-treated Tr1 cells also resulted in suppressed clinical scores and demyelination when adoptively transferred into mice with experimental allergic encephalomyelitis. Furthermore, analysis of the cytokine profile indicated that there were two differential reaction patterns during the B7H1-Ig-induced Tr1 development. These two patterns were characterized by activation of IFN-gammaR+ IL-10R- Th1 and IFN-gammaR+ IL-10R+ Tr1 cells, respectively. Secretion of IFN-gamma by Th1 and the expression of IFN-gammaR on Tr1 were critical for further Tr1 differentiation, as demonstrated by mAb blocking and by analysis in IFN-gamma(-/-) mice. In conclusion, B7H1 is capable of inducing Tr1 differentiation from naive CD4+ T cells by coactivation in an IFN-gamma- or Th1-dependent manner. Our study may shed some light upon the clinical usage of B7H1 as a therapeutic reagent for induction of tolerance.     

NK T cell-derived IL-10 is essential for the differentiation of antigen-specific T regulatory cells in systemic tolerance

In a model of systemic tolerance called Anterior Chamber-Associated Immune Deviation (ACAID), the differentiation of the T regulatory (Tr) cells depends on NK T cells and occurs in the spleen. We now show that the CD1d-reactive NK T cell subpopulation, required for development of systemic tolerance, expresses the invariant V alpha 14J alpha 281 TCR because J alpha 281 knockout (KO) mice were unable to generate Ag-specific Tr cells and ACAID. The mechanism for NK T cell-dependent differentiation of Ag-specific Tr cells mediating systemic tolerance was studied by defining the cytokine profiles in heterogeneous and enriched NK T spleen cells. In contrast to there being no differences in most regulatory cytokine mRNAs, both mRNA and protein for IL-10 were increased in splenic NK T cells of anterior chamber (a.c.)-inoculated mice. However, IL-10 mRNA was not increased in spleens after i.v. inoculation. Finally, NK T cells from wild-type (WT) mice, but not from IL-10 KO mice, reconstituted the ACAID inducing ability in J alpha 281 KO mice. Thus, NK T cell-derived IL-10 is critical for the generation of the Ag-specific Tr cells and systemic tolerance induced to eye-inoculated Ags.     

Antigen-specific regulatory T cells develop via the ICOS-ICOS-ligand pathway and inhibit allergen-induced airway hyperreactivity

Asthma is caused by T-helper cell 2 (Th2)-driven immune responses, but the immunological mechanisms that protect against asthma development are poorly understood. T-cell tolerance, induced by respiratory exposure to allergen, can inhibit the development of airway hyperreactivity (AHR), a cardinal feature of asthma, and we show here that regulatory T (T(R)) cells can mediate this protective effect. Mature pulmonary dendritic cells in the bronchial lymph nodes of mice exposed to respiratory allergen induced the development of T(R) cells, in a process that required T-cell costimulation via the inducible costimulator (ICOS-ICOS-ligand pathway. The T(R) cells produced IL-10, and had potent inhibitory activity; when adoptively transferred into sensitized mice, T(R) cells blocked the development of AHR. Both the development and the inhibitory function of regulatory cells were dependent on the presence of IL-10 and on ICOS-ICOS-ligand interactions. These studies demonstrate that T(R) cells and the ICOS-ICOS-ligand signaling pathway are critically involved in respiratory tolerance and in downregulating pulmonary inflammation in asthma.     

Intravenous injection of a D1 protein of the Smith proteins postpones murine lupus and induces type 1 regulatory T cells

T cells that recognize nucleoproteins are required for the production of anti-dsDNA Abs involved in lupus development. SmD1 83-119 (a D1 protein of the Smith (Sm) proteins, part of small nuclear ribonucleoprotein) was recently shown to provide T cell help to anti-dsDNA Abs in the NZB/NZW model of lupus. Using this model in the present study, we showed that high dose tolerance to SmD1 (600-1000 microg i.v. of SmD1(83-119) peptide/mo) delays the production of autoantibodies, postpones the onset of lupus nephritis as confirmed by histology, and prolongs survival. Tolerance to SmD1 83-119 was adoptively transferred by CD90+ T cells, which also reduce T cell help for autoreactive B cells in vitro. One week after SmD1 83-119 tolerance induction in prenephritic mice, we detected cytokine changes in cultures of CD90+ T and B220+ B cells with decreased IFN-gamma and IL-4 expression and an increase in TGFbeta. Increased frequencies of regulatory IFN-gamma+ and IL10+ CD4+ T cells were later detected. Such regulatory IL-10+/IFN-gamma+ type 1 regulatory T cells prevented autoantibody generation and anti-CD3-induced proliferation of naive T cells. In conclusion, these results indicate that SmD1 83-119 peptide may play a dominant role in the activation of helper and regulatory T cells that influence autoantibody generation and murine lupus.