Regulatory activity of human CD4 CD25 T cells depends on allergen concentration, type of allergen and atopy status of the donor

Discrepancy in the suppressive function of regulatory T cells in allergic asthmatic vs. allergic rhinitis subjects upon low-dose allergen challenges

Background

Regulatory T cells (Tregs) contribute to the maintenance of immunological tolerance. There is evidence of impaired function of these cells in people with asthma and allergy. In this study, we evaluated and compared the function of Tregs in allergic asthmatic and allergic non-asthmatic patients, both before and after low-dose allergen challenges.

Methods

Three groups of subjects were recruited for a baseline evaluation: healthy controls without allergy or asthma, allergic asthmatic subjects, and allergic non-asthmatic subjects. All of them were subjected to expiratory flow measurements, sputum induction, and blood sampling. In addition, both groups of allergic subjects underwent low-dose allergen challenges. Tregs were isolated from whole blood using CD4+CD25high and CD127low staining. The suppression function was measured by flow cytometry. The levels of IL-10, IFN-γ, IgG4, IgA, and TGF-β were measured using ELISA, and sputum Foxp3 was evaluated using qRT-PCR.

Results

The suppressive function of Tregs in healthy controls was significantly higher than in allergic asthmatic or allergic non-asthmatic subjects. Repeated exposure to low doses of allergen increased the suppressor function of Tregs in allergic non-asthmatic subjects but decreased it in allergic asthmatic subjects. Foxp3 gene expression was increased in induced sputum in allergic non-asthmatic subjects, whereas it did not change in asthmatic subjects. Serum IL-10 level was decreased in allergic asthmatic subjects after allergen challenge but not in allergic non-asthmatic subjects. IFN-γ level increased upon allergen challenge in allergic non-asthmatic subjects. IgG4 level was higher in allergic non-asthmatic subjects than in allergic asthmatic subjects.

Conclusions

Low-dose allergen challenges stimulate the suppressor function of Tregs in non-asthmatic allergic subjects but not in allergic asthmatic subjects.

Current Strategies to Modulate Regulatory T Cell Activity in Allergic Inflammation

Over the past decades, atopic diseases, including allergic rhinitis, asthma, atopic dermatitis, and food allergy, increased strongly worldwide, reaching up to 50% in industrialized countries. These diseases are characterized by a dominating type 2 immune response and reduced numbers of allergen-specific regulatory T (Treg) cells. Conventional allergen-specific immunotherapy is able to tip the balance towards immunoregulation. However, in mouse models of allergy adaptive transfer of Treg cells did not always lead to convincing beneficial results, partially because of limited stability of their regulatory phenotype activity. Besides genetic predisposition, it has become evident that environmental factors like a westernized lifestyle linked to modern sanitized living, the early use of antibiotics, and the consumption of unhealthy foods leads to epithelial barrier defects and dysbiotic microbiota, thereby preventing immune tolerance and favoring the development of allergic diseases. Epigenetic modification of Treg cells has been described as one important mechanism in this context. In this review, we summarize how environmental factors affect the number and function of Treg cells in allergic inflammation and how this knowledge can be exploited in future allergy prevention strategies as well as novel therapeutic approaches.

Understanding of the Molecular Mechanisms of Allergy

The prevalence of allergic disease has dramatically increased over the past 30 years in Westernized countries. It is unlikely that the rapid increase in the prevalence of allergic disease is the result of genetic changes, which highlights the importance of environmental factors in the development of allergic disease. The "hygiene hypothesis" was put forward in 1989 and focused attention on the notion that exposure to microbes and their products in early life can modify the risk for development of allergic disease. Infections were thought to polarize the immunological response toward a Th2-mediated immune response causing allergic disease. However, it is likely that the Th1/Th2 imbalance is too simplistic to explain the increased prevalence of allergic disease. Current research is focusing on understanding the role of T-regulatory cells in inducing a state of tolerance and the resulting modified Th2 response observed in natural and induced tolerance.

Rhynchophyllin attenuates neuroinflammation in Tourette syndrome rats via JAK2/STAT3 and NF-κB pathways

The aim of this study was designed to investigate the effects of rhynchophyllin (RH) on neuroinflammation in Tourette syndrome (TS) rats. TS model was established in rats by the injection of selective 5-HT2A/2C agonist 1-(2, 5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI). Behavior in DOI-induced rats was tested. Inflammatory cytokines levels such as interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) in serum and striatum were detected. The expression levels of janus kinase 2 (JAK2)/signal transducer and transcription activator 3 (STAT3) and nuclear factor (NF)-κB pathways in striatum were measured by Western blot. Data indicated that RH can significantly reduce the numbers of nodding experiment of TS rats. RH significantly decreased IL-6, IL-1β, and TNF-α in serum and striatum of TS rats, with altered expression of P-JAK2, P-STAT3, P-NF-κBp65, and P-IκBα in TS rats, as evidenced by Western blot analysis and immunohistochemistry, suggesting that the regulation of JAK2/STAT3 and NF-κB pathways might be involved in the mechanism of RH on TS.

Increased gene expression of inflammatory markers in nasal turbinate of patients with persistent allergic rhinitis and chronic obstruction

PURPOSE

The pathogenesis of persistent allergic rhinitis with chronic and refractory nasal obstruction is still unknown. Inflammation and tissue remodeling are known to play a role, but this has not been studied thoroughly. The purpose of this study is to identify the profile of gene expression of inflammatory and remodeling markers in nasal mucosa of patients with PAR and chronic obstruction.

METHODS

After informed consent, we obtained nasal mucosa tissue from five aeroallergen-sensitized PAR patients undergoing anterior turbinectomy, and control non-sensitized individuals undergoing cerebrospinal fluid fistula repair or rhinoplasty. We assessed the expression of 34 genes related to inflammation and tissue remodeling using the real-time polymerase chain reaction (qPCR) to quantify each mRNA.

RESULTS

IL-4 mRNA was upregulated in nasal mucosa of all five patients; CCR3, CCR8 and Eotaxin-2 were upregulated in four out of five patient samples; while IL-5 and IL-13 were upregulated in two of them. TGF-β1 was not upregulated in PAR samples. mRNA from metalloproteinases MMP-7, MMP13 and MMP15 were upregulated in three out of five samples. Our results indicate a typical mRNA expression profile of the infiltrating inflammatory Th2 cells and eosinophils, combined with altered gene expression of remodeling-related proteins in stromal cells from the mucosa.

CONCLUSION

Prolonged allergen challenge can lead to persistent upregulation of genes for inflammatory mediators such as IL-4 Th2/eosinophil cytokines, chemokines and receptors, which may play an important role in maintaining PAR with chronic nasal obstruction. Our findings may have therapeutic implications, including the use of anti-IL4, -CCR3 or -MMP therapy to ameliorate the condition.

Rhynchophylline Attenuates Tourette Syndrome via BDNF/NF-κB Pathway In Vivo and In Vitro

Tourette syndrome (TS) is characterized by one of the chronic neuropsychiatric disorders in multiple children, and the pathogenesis of Tourette syndrome (TS) has not been previously elucidated.The aim of this study was designed to investigate the effects of rhynchophylline (RH) on Tourette syndrome (TS) in rats.TS model was established in rats and BV2 cells by the selective 5-HT2A/2C agonist 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI). Behavior evaluations including stereotypy recording and autonomic activity test were performed. Inflammatory cytokine levels such as interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) in serum, striatum, and cell supernatant were detected. The expression levels of BDNF/NF-κB pathway in striatum and BV2 cells were measured by Western blot. Dopamine (DA) and dopamine receptor D 2 (D2) in striatum were also measured.Data indicated that RH significantly decreased IL-6, IL-1β, and TNF-α in serum, striatum, and cell supernatant of TS model, with altered expression of P-NF-κBp65, P-IκBα, and BDNF in TS rats, and DOI-induced BV2 cells, as evidenced by Western blot analysis and immunohistochemistry analysis. RH also significantly reduced the levels of DA and D2 in striatum.Our results shown that the regulation of BDNF/NF-κB pathway might be involved in the effects of RH on TS model.

Effects of allergen-specific immunotherapy on peripheral blood regulatory T cells and serum concentrations of cytokines and immunoglobulins in horses with allergic dermatitis

The aim of this study was to assess the effect of allergen-specific immunotherapy (ASIT) on the immunological responses of horses. Blood samples were taken from thirty-two horses with allergic dermatitis treated with ASIT and 10 healthy control horses at 0, 3, 6, 9 and 12 months to investigate the evolution of the percentage of regulatory T cells (Treg) in the peripheral blood and the serum levels of cytokines and immunoglobulins. Clinical improvement was appreciated by the majority of the horses' owners (56.6%). No effect of ASIT on CD4⁺CD25^High Treg cells was found during the one year treatment period. No differences in the percentage of CD4⁺ T cells were observed between the groups, and no effects of ASIT over time were observed. The percentage of CD25⁺ T cells was always higher in the ASIT group (17.9 ± 11.3%) than in the control group (7.3 ± 4.4%, p < 0.001). We did not detect any effect of ASIT on the serum levels of TGF-β, IL-10 and IFN-γ or on the serum concentrations of IgA and IgG4. A reduction in the serum levels of total IgE in the horses with allergic dermatitis was observed at the 6th month (p < 0.05), but increased again at the end of the study. The results indicate that immunotherapy was insufficient to induce significant changes that could indicate T cell tolerance, a shift in cytokine production to more protective Th1 cells. More studies are needed with new vaccine compositions and administration protocols to improve the immunological responses of the horses with allergic dermatitis.

Lymphocytic, cytokine and transcriptomic profiles in peripheral blood of dogs with atopic dermatitis

Background

Canine atopic dermatitis (cAD) is a common chronic and pruritic skin disease in dogs. The development of cAD involves complex interactions between environmental antigens, genetic predisposition and a number of disparate cell types. The aim of the present study was to perform comprehensive analyses of peripheral blood of AD dogs in relation to healthy subjects in order to determine the changes which would be characteristic for cAD.

Results

The number of cells in specific subpopulations of lymphocytes was analyzed by flow cytometry, concentration of chosen pro- and anti-inflammatory cytokines (IL-4, IL-10, IL-13, TNF-α, TGF-β1) was determined by ELISA; and microarray analysis was performed on RNA samples isolated from peripheral blood nuclear cells of AD and healthy dogs. The number of Th cells (CD3⁺CD4⁺) in AD and healthy dogs was similar, whereas the percentage of Tc (CD3⁺CD8⁺) and Treg (CD4⁺CD25⁺ Foxp3⁺) cells increased significantly in AD dogs. Increased concentrations of IL-13 and TNF-α, and decreased levels of IL-10 and TGF-β1 was observed in AD dogs. The level of IL-4 was similar in both groups of animals. Results of the microarray experiment revealed differentially expressed genes involved in transcriptional regulation (e.g., transcription factors: SMAD2, RORA) or signal transduction pathways (e.g., VEGF, SHB21, PROC) taking part in T lymphocytes lineages differentiation and cytokines synthesis.

Conclusions

Results obtained indicate that CD8⁺ T cells, beside CD4⁺ T lymphocytes, contribute to the development of the allergic response. Increased IL-13 concentration in AD dogs suggests that this cytokine may play more important role than IL-4 in mediating changes induced by allergic inflammation. Furthermore, observed increase in Treg cells in parallel with high concentrations of TNF-α and low levels of IL-10 and TGF-β1 in the peripheral blood of AD dogs point at the functional insufficiency of Treg cells in patients with AD.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-016-0805-6) contains supplementary material, which is available to authorized users.

Analysis of allergic immune responses in humanized mice

Nowadays, more than 25% of the population in industrial countries are affected by IgE-mediated (atopic) allergic diseases such as allergic rhinitis, asthma and atopic eczema. Due to intensive research on basis of in vitro studies with human immune cells and different murine in vivo models of allergy fundamental mechanisms of allergic immune responses have been elucidated during the last years. However, human studies are restricted and the immune system of mice differs from the human immune system in several aspects so that the transferability of experimental results from mice to men is limited. Humanized mice represent a new tool to analyze the interaction of human immune cells under physiological conditions as far as possible, particularly to test novel therapeutic strategies. This review summarizes the impact of humanized mouse models for the investigation and treatment of allergic diseases.

Raised immunoglobulin A and circulating T follicular helper cells are linked to the development of food allergy in paediatric liver transplant patients

BACKGROUND

Post-transplant food allergy (LTFA) is increasingly observed after paediatric liver transplantation (LT). Although the immunopathology of LTFA remains unclear, immunoglobulin (Ig) E seems to be implicated.

OBJECTIVE

To study humoral and cellular immunity in paediatric LT patients in search for factors associated with LTFA, and compare with healthy controls (HC) and non-transplant food-allergic children (FA).

METHODS

We studied serum Ig levels in 29 LTFA, 43 non-food-allergic LT patients (LTnoFA), 21 FA patients and 36 HC. Serum-specific IgA and IgE against common food allergens in LTFA, IgA1 , IgA2 and joining-chain-containing polymeric IgA (pIgA) were measured. Peripheral blood mononuclear cells were analysed by flow cytometry for B and T cell populations of interest.

RESULTS

Serum IgA and specific IgA were higher in LTFA compared to LTnoFA. LTFA patients had the highest proportion of circulating T follicular helper cells (cTfh). The percentage of cTfh correlated positively with serum IgA. Unique in LTFA was also the significant increase in serum markers of mucosal IgA and the decrease in the Th17 subset of CXCR5(-) CD4(+) cells compared to HC. Both LT patients exhibited a rise in IgA(+) memory B cells and plasmablasts compared to HC and FA.

CONCLUSIONS

LT has an impact on humoral immunity, remarkably in those patients developing FA. The increase in serum markers of mucosal IgA, food allergen-specific IgA and cTfh cells observed in LTFA, point towards a disturbance in intestinal immune homoeostasis in this patient group.

Inhaled corticosteroid use is associated with increased circulating T regulatory cells in children with asthma

BACKGROUND

T regulatory (Treg) cells are important in balancing immune responses and dysregulation of Treg cells has been implicated in the pathogenesis of multiple disease states including asthma. In this study, our primary aim was to determine Treg cell frequency in the peripheral blood of children with and without asthma. The secondary aim was to explore the association between Treg cell frequency with allergen sensitization, disease severity and medication use.

METHODS

Peripheral blood mononuclear cells from healthy control subjects (N = 93) and asthmatic children of varying disease severity (N = 66) were characterized by multi-parameter flow cytometry.

RESULTS

Our findings demonstrate that children with asthma had a significantly increased frequency of Treg cells compared to children without asthma. Using a multivariate model, increased Treg cell frequency in children with asthma was most directly associated with inhaled corticosteroid use, and not asthma severity, allergic sensitization, or atopic status of the asthma.

CONCLUSION

We conclude that low dose, local airway administration of corticosteroids is sufficient to impact the frequency of Treg cells in the peripheral blood. These data highlight the importance of considering medication exposure when studying Treg cells and suggest inhaled corticosteroid use in asthmatics may improve disease control through increased Treg cell frequency.

House dust allergy and immunotherapy

HDM allergy is associated with asthma, allergic rhinitis and atopic dermatitis. In many countries childhood asthma is predominantly found in HDM-allergic children with their probability of developing disease being proportional to their IgE antibody titers and the early development of Th2 responses. While the pathogenesis is complex and increasingly linked to infection the immunologically-based allergen immunotherapy and anti-IgE antibody therapy are highly beneficial. Immunotherapy could be a short-term treatment providing lifelong relief but the current regimens depend on repeated administration of allergen over years. Immunological investigations point to a contribution of responses outside the Th2 pathway and multiple potential but unproven control mechanisms. Over half of the IgE antibodies are directed to the group 1 and 2 allergens with most of remainder to the group 4, 5, 7 and 21 allergens. This hierarchy found in high and low responders provides a platform for introducing defined allergens into immunotherapy and defined reagents for investigation.

Environment and T regulatory cells in allergy

The central role of T regulatory cells in the responses against harmless environmental antigens has been confirmed by many studies. Impaired T regulatory cell function is implicated in many pathological conditions, particularly allergic diseases. The "hygiene hypothesis" suggests that infections and infestations may play a protective role for allergy, whereas environmental pollutants favor the development of allergic diseases. Developing countries suffer from a variety of infections and are also facing an increasing diffusion of environmental pollutants. In these countries allergies increase in relation to the spreading use of xenobiotics (pesticides, herbicides, pollution, etc.) with a rate similar to those of developed countries, overcoming the protective effects of infections. We review here the main mechanisms of non-self tolerance, with particular regard to relations between T regulatory cell activity, infections and infestations such as helminthiasis, and exposure to environmental xenobiotics with relevant diffusion in developing countries.

MicroRNA-23b promotes tolerogenic properties of dendritic cells in vitro through inhibiting Notch1/NF-κB signalling pathways

BACKGROUND

MicroRNAs (miRNAs) are known to regulate the inflammatory response in various cell types. However, the ability of miRNAs to modulate dendritic cells (DCs) function for allergen immunotherapy is unclear.

OBJECTIVE

To assess the role of miR-23b in the regulation of ovalbumin (OVA)-induced DC differentiation and function and to investigate the related molecular mechanisms.

METHODS

Bone marrow-derived dendritic cells (BMDCs) were generated from murine bone marrow progenitor cells and subsequently stimulated with OVA to examine the profile of miRNA expression. After transfection with miR-23b reagents, DCs were evaluated for endocytic ability, surface marker expression, cytokine secretion and CD4+ T-cell differentiation. The possible roles of the Notch and NF-κB signalling pathways were also evaluated. Human monocyte-derived dendritic cells (MDDCs) were similarly evaluated as well.

RESULTS

Significant upregulation of miR-23b was observed in BMDCs pulsed with OVA. Following miR-23b transfection, BMDCs showed decreased OVA uptake, increased IL-10 production, decreased IL-12 production and an enhanced capacity to promote FoxP3+ CD4+ T regulatory cells (Tregs) differentiation. In addition, inactivation of the Notch1 and NF-κB signalling pathways were observed. Conversely, inhibition of miR-23b in BMDCs resulted in the opposite effects. In human MDDCs, miRNA23b transfection similarly increased IL-10 and decreased IL-12 production, and that treated human MDDCs induced increased FoxP3+ CD4+ T cells.

CONCLUSION

Our findings provide evidence that miR-23b is capable of inducing tolerogenic DC activity and Treg responses in vitro through the inhibition of the Notch1 and NF-κB signalling pathways; thus, miR-23b might represent a therapeutic target for the management of allergic diseases.

Changes in thymic regulatory T-cell maturation from birth to puberty: differences in atopic children

BACKGROUND

Characterization of regulatory immune pathways is a research priority for both the pathogenesis of allergic disease and potential therapeutic strategies.

OBJECTIVE

The thymus is a rich source of regulatory T (Treg) cells, which offers a novel opportunity to document the maturation of these pathways beyond limited studies on small volumes of peripheral blood available from young children.

METHODS

Thymus tissue was collected from children undergoing cardiac surgery (age, 1 week to 14 years), and skin prick testing was performed from 12 months of age. The ontogeny of Treg cell maturation and function was examined in atopic (n = 20) and nonatopic (n = 20) children by assessing their phenotype, enumeration, proliferation, and suppressive ability.

RESULTS

Age-related changes in the thymic cytokine milieu paralleled the changes seen in peripheral immune function. Specifically, the thymic microenvironment is similarly T(H)2 skewed during the early postnatal period, and this undergoes age-related suppression as the T(H)1 (IFN-γ) response increased. We detected CD4(+)CD25(+)CD127(lo/-) forkhead box protein 3 (FOXP3)-positive Treg cells in the neonatal thymus. These cells suppressed the proliferative response to allogeneic stimulation of CD4(+)CD25(-) T cells dose dependently. In nonatopic children Treg cell turnover and suppressive function increased with age and paralleled the increase in global thymic FOXP3 mRNA expression, whereas in atopic children Treg cell maturation was significantly delayed compared with that seen in age-matched nonatopic children.

CONCLUSION

These data suggest that the developmental changes in the thymus parallel the recognized changes in peripheral blood responses. There is also a developmental delay in the function of thymic regulatory cells in atopic compared with nonatopic children. These differences are fundamental to understanding early events that lead to immune dysregulation and might predispose to allergic disease.

The presence of B7-H4+ macrophages and CD25+CD4+ and FOXP3+ regulatory T cells in the microenvironment of nasal polyps - a preliminary report

The nasal polyp (NP) seems to represent the end-stage of longstanding inflammation in patients with chronic rhinosinusitis. The aim of our study has been to evaluate the presence of two regulatory cell populations in the microenvironment of NP: CD4+CD25high Foxp3+ (Treg) cells and B7-H4-expressing macrophages. Treg cells are actively able to inhibit T lymphocytes, while the population of B7-H4-expressing macrophages has recently been described as characterized by a regulatory function similar to that of Treg cells. For our study, we evaluated 14 NP tissue samples. The samples were divided into two main groups, eosinophilic (NP) and lymphocytic (NP), according to the predominant type of immune cell infiltration. The presence of Treg cells and B7-H4 positive macrophages in the samples was analyzed by FACS. Treg cells and B7-H4-expressing macrophages were identified in all the examined nasal polyps. The percentages of both Treg cells and of B7H4 positive cells found in the eosinophilic nasal polyps were higher than those found in the lymphocytic nasal polyps. Treg cells and B7H4+ macrophage subpopulations were present in the NP microenvironment and the alterations in their percentages were related to a distinct pattern of immune cell infiltration.

Mechanisms of subcutaneous allergen immunotherapy

Allergen-specific immunotherapy (SIT) is the only curative approach in the treatment of allergic diseases defined up-to-date. Peripheral T-cell tolerance to allergens, the goal of successful allergen-SIT, is the primary mechanism in healthy immune responses to allergens. By repeated administration of increased doses of the causative allergen, allergen-SIT induces a state of immune tolerance to allergens through the constitution of T regulatory (Treg) cells, including allergen-specific interleukin (IL)-10-secreting Treg type 1 cells and CD4(+)CD25(+)Treg cells; induction of suppressive cytokines, such as IL-10 and transforming growth factor β; suppression of allergen-specific IgE and induction of IgG4 and IgA; and suppression of mast cells, basophils, eosinophils, and inflammatory dendritic cells. This review summarizes the current knowledge on the mechanisms of allergen-SIT with emphasis on the roles of Treg cells in allergen-SIT.

TLR2 polymorphisms influence neonatal regulatory T cells depending on maternal atopy

BACKGROUND

Toll-like receptor (TLR) polymorphisms have been associated with atopic diseases in children and adults. Development of atopic diseases may be modified by TLR-mediated signals that modulate T-regulatory cells (Tregs) early in life when maternal influences are still present and relevant. The aim of this study was to assess whether genetic TLR variants influence Tregs in neonates.

METHODS

Twelve single nucleotide polymorphisms located in TLR1, TLR2, TLR4, TLR6, and TLR10 were genotyped in 200 cord blood samples (72 samples from atopic, 128 from nonatopic mothers). Cord blood mononuclear cells were cultured without or with stimulation [lipid A (LpA), peptidoglycan (Ppg), phytohemagglutinin, house dust mite]. mRNA expression of Treg marker genes [forkhead box protein P3 (FOXP3), glucocorticoid-induced tumor necrosis factor receptor (GITR), lymphocyte activation gene 3 (LAG3)], TLR2, Th1/Th2 cytokines, and tumor necrosis factor alpha (TNF-α) was measured.

RESULTS

In children with the AA genotype of the TLR2 promoter variant rs4696480, gene expression of FOXP3 and Treg marker genes GITR and LAG3 as well as Th2 cytokines and TNF-α secretion was significantly increased in the presence of maternal atopy and Tregs decreased without maternal atopy. In carriers of the GG genotype for TLR2 rs1898830, gene expression of Treg marker genes was significantly decreased with and increased without maternal atopy. FOXP3 expression was also modified by TLR1 rs4833095 (P ≤ 0.03) and trendwise by TLR10 rs4129009 after LpA and Ppg stimulation.

CONCLUSIONS

Genetic variations of TLR2, TLR1, and TLR10 affect Treg marker gene expression in cord blood. Gene-immunological interactions of the TLR pathway influence Tregs early in life, modulated by maternal atopy. This may be relevant for immune maturation in the development of atopic diseases in childhood.

From allergen genes to allergy vaccines

IgE-mediated allergy is a hypersensitivity disease affecting more than 25% of the population. The structures of the most common allergens have been revealed through molecular cloning technology in the past two decades. On the basis of this knowledge of the sequences and three-dimensional structures of culprit allergens, investigators can now analyze the immune recognition of allergens and the mechanisms of allergic inflammation in allergic patients. Allergy vaccines have been constructed that are able to selectively target the aberrant immune responses in allergic patients via different pathways of the immune system. Here we review various types of allergy vaccines that have been developed based on allergen structures, results from their clinical application in allergic patients, and future strategies for allergen-specific immunotherapy and allergy prophylaxis.

Infiltration of Foxp3- and Toll-like receptor-4-positive cells in the intestines of children with food allergy

OBJECTIVES

Regulatory T (Treg) cells together with intestinal microflora play a central role in controlling allergic inflammation. We examined the markers related to Treg cells, and bacterial signaling, such as Toll-like receptors (TLR)-2 and -4, in the duodenal mucosa of patients with food allergy (FA).

PATIENTS AND METHODS

Small intestinal samples were collected from patients with FA on a normal or an elimination diet, from healthy controls and patients with untreated celiac disease. Single and double immunohistochemistry were used to enumerate the densities of Foxp3-positive cells and TLR2- and TLR4-positive cells in the mucosa and evaluate the colocalization of Foxp3 expression in CD4, CD25, and CTLA-4 cells. The mRNA expression of CD25, Foxp3, TLR2, and TLR4 was measured by reverse transcriptase-polymerase chain reaction.

RESULTS

The densities of Foxp3 and TLR4 cells were significantly increased in patients with untreated FA compared with healthy controls (P = 0.003, P = 0.033), and the Foxp3 cells were higher in untreated than in treated allergic patients (P < 0.001). The immense majority of Foxp3 cells were CD4 (median 100%), CTLA-4 (100%), or CD25 (81%). The ratio of Foxp3 mRNA to Foxp3 cells was decreased in patients with FA and in patients with celiac disease compared with controls (P = 0.036, P = 0.035).

CONCLUSIONS

Foxp3 cells are increased in the duodenum of patients with untreated FA, but these cells are not able to suppress the harmful immune response, indicated by the low expression of Foxp3 transcripts. The increase of TLR4 cells and their correlation with TCRgammadelta intraepithelial lymphocytes suggest a role for the innate immunity and intestinal microbiota in FA.

Regulatory T cells in prenatal blood samples: variability with pet exposure and sensitization

Fetal exposures have come under investigation as risk factors of early life allergic disease. In this study we aimed to examine the relationships between dog or cat exposure and naturally occurring regulatory T cells (Treg cells), thought to play an important role in immune tolerance, in pregnant women. A cross-sectional analysis was conducted among 204 pregnant women who were queried regarding dog and cat exposure. Treg cells (CD4+CD25+Foxp3+ lymphocytes) and allergen-specific IgE were measured in venous blood samples. Atopy was defined as allergen-specific IgE > or =0.35kU/l reactive with common allergens including dust mite, dog, cat, Timothy grass, ragweed, Alternaria alternata, egg white or cockroach. Nonparametric Wilcoxon rank sum tests and linear regression models of log transformed Treg cell levels were used in analyses. Among women sensitized to dog, those who had a dog or cat in the home had lower Treg cell levels compared with those who had no dog or cat. However, among women not sensitized to dog, those with a dog or cat in the home had higher Treg cell levels compared with those who did not. Among women sensitized to cat, those who had a dog or cat in the home had lower Treg cell levels compared with those who had no dog or cat. Gestational age at blood draw did not affect the associations. We conclude that Treg cell levels during pregnancy vary in association with both dog and cat exposure and atopic status.

Pathogenic mechanisms of allergic inflammation: atopic asthma as a paradigm

Prospective studies tracking birth cohorts over periods of years indicate that the seeds for atopic asthma in adulthood are sewn during early life. The key events involve programming of functional phenotypes within the immune and respiratory systems which determine long-term responsiveness to ubiquitous environmental stimuli, particularly respiratory viruses and aeroallergens. A crucial component of asthma pathogenesis is early sensitization to aeroallergens stemming from a failure of mucosal tolerance mechanisms during the preschool years, which is associated with delayed postnatal maturation of a range of adaptive and innate immune functions. These maturational defects also increase risk for severe respiratory infections, and the combination of sensitization and infections maximizes risk for early development of the persistent asthma phenotype. Interactions between immunoinflammatory pathways stimulated by these agents also sustain the disease in later life as major triggers of asthma exacerbations. Recent studies on the nature of these interactions suggest the operation of an infection-associated lung:bone marrow axis involving upregulation of FcERlalpha on myeloid precursor populations prior to their migration to the airways, thus amplifying local inflammation via IgE-mediated recruitment of bystander atopic effector mechanisms. The key participants in the disease process are airway mucosal dendritic cells and adjacent epithelial cells, and transiting CD4(+) effector and regulatory T-cell populations, and increasingly detailed characterization of their roles at different stages of pathogenesis is opening up novel possibilities for therapeutic control of asthma. Of particular interest is the application of genomics-based approaches to drug target identification in cell populations of interest, exemplified by recent findings discussed below relating to the gene network(s) triggered by activation of Th2-memory cells from atopics.

Low-dose cyclosporine A therapy increases the regulatory T cell population in patients with atopic dermatitis

BACKGROUND

Atopic dermatitis (AD) is a T cell dependent chronic relapsing inflammatory skin disorder successfully treated with cyclosporine A (CsA). Clinical observations indicate that even low-dose CsA therapy is successful in severely affected AD patients. We studied the impact of low-dose CsA therapy on the ability of T helper cells to be activated, and examined whether regulatory T (Treg) cells are increased in these patients.

METHODS

Peripheral T cells were activated in a whole blood sample and interleukin-2 producing cells were measured by intracellular cytokine staining. Regulatory T cells were analyzed by intracellular FoxP3 staining. Regulatory T cells (CD4(+)CD25(+)CD127(low)) and effector T cells (CD4(+)CD25(-)CD127(+)) were sorted by flow cytometry and used for suppression assays.

RESULTS

A group of AD patients treated with low-dose CsA had a significantly larger Treg cell population than a healthy control subject group. In individual patients, onset of low-dose CsA therapy reduced the ability of T cells to be activated to 42 +/- 18% (P < 0.005) and significantly increased Treg cells, both in absolute numbers (1.6-fold change) and frequencies (1.7-fold change). Treg cells from AD patients showed similar suppressive capacities as Treg cells from healthy donors. Furthermore, Treg cells from AD patients had skin homing properties.

CONCLUSION

Our results indicate that the therapeutic effect of low-dose CsA therapy in AD patients might be not only mediated by the inhibition of T cell hyperactivity but also by an increased population of Treg cells.

Analysis of T-helper responses and FOXP3 gene expression in patients with Japanese cedar pollinosis

BACKGROUND

Evidence has been accumulated indicating that regulatory T (T-reg) cells play a crucial role in the maintenance of peripheral T-cell tolerance to allergens. To explore the role of FOXP3, which is required for the development of T-reg cells, in allergen-specific immune responses, we examined the relationship between the alteration of FOXP3 gene expression and in vitro immune responses against allergens.

METHODS

Peripheral blood mononuclear cells obtained from 19 human histocompatibility leukocyte antigens (HLA)-DPB1*0501 donors, including patients with Japanese cedar pollinosis and nonallergic healthy donors, were stimulated with Cry j 1 p61-75 peptide. On day 7, T cells were tested for peptide-specific reactivity in IFN-gamma and interleukin (IL)-5 enzyme-linked immunospot (ELISPOT) assays. Real-time quantitative RT-PCR was performed to assess relative change of FOXP3 gene expression before and after in vitro stimulation. Neutralization assays using anti-glucocorticoid-induced tumor necrosis factor receptor family-related protein (GITR) and anti-IL-10 monoclonal antibody were also performed.

RESULTS

Of 14 patients with allergic pollinosis tested, 10 responders displayed T-helper type 2 (Th2)-polarized reactivity to Cry j 1 p61-75, and 2 donors showed Th0 responses. Notably, the change of FOXP3 gene expression in donors showing peptide-specific T-helper responses was significantly lower than that in nonresponders, regardless of allergic pollinosis.

CONCLUSION

Our data indicate that FOXP3 is functional in nonallergic healthy donors as well as allergic patients, and FOXP3-expressing T cells may be responsible for the down-regulation of allergen-specific T-helper responses in individuals. A better understanding of the nature and specificity of FOXP3-expressing T cells in a suppressive mechanism is necessary to develop new immunotherapies against allergic rhinitis.

Does hapten exposure predispose to atopic disease? The hapten-atopy hypothesis

Contact allergy data indicates that atopics have heightened oral tolerance to haptens (chemical allergens). We speculate here, that artificially increased oral exposure to chemicals compete with dietary proteins for the development of oral tolerance, predisposing to the acquisition of food protein allergy and representing one driver for the increasing prevalence of protein allergy and/or atopy. Hapten exposure via other surfaces such as the skin and airways might also be important in promoting atopic disease. Consistent with this hypothesis it is notable that over 40 years, with the huge increase in atopic disease, there has also been an increase in dietary hapten exposure through processed food, formula milk and oral antibiotic and drug use.

Children with egg allergy have evidence of reduced neonatal CD4(+)CD25(+)CD127(lo/-) regulatory T cell function

BACKGROUND

The role of regulatory T (Treg) cells in allergic predisposition is not known.

OBJECTIVE

This study compared the frequency and function of cord blood Treg cells from nonallergic children (n = 18) with those from children who have egg allergy (n = 15) in the first year of life.

METHODS

CD4(+) effector T cells and autologous antigen-presenting cells isolated from cord blood mononuclear cells were cocultured with or without CD4(+)CD25(+)CD127(lo/-) Treg cells, and cytokine responses to staphylococcal endotoxin B were assessed after 48 hours.

RESULTS

The addition of Treg cell populations to cord blood mononuclear cell cultures resulted in significant reduction in IL-10 (P = .002), IL-13 (P = .012), and IFN-gamma (P < .001) production. Consistent with other reports, effector CD4(+) T-cell responses (IFN-gamma and IL-13) tended to be lower in the allergic group. These neonates showed less significant Treg cell-associated suppression of IFN-gamma (P = .015) compared with that seen in the nonallergic group (P = .001). The allergic group was also less likely (44%) to show Treg cell-associated suppression of IFN-gamma effector responses compared with that seen in the nonallergic group (78%, P = .015). The magnitude of suppression (change in IFN-gamma level when CD4(+)CD25(+)CD127(lo/-) Treg cells were added to responding effector T-cell cultures) was significantly lower in the allergic group (P = .004). There were no between-group differences in the circulating CD4(+)CD25(+)CD127(lo/-) Treg cells (as a percentage of cord blood T cells) or in the FOXP3 expression of these cells.

CONCLUSION

This study confirms the presence and activity of Treg cells in cord blood and provides preliminary evidence of differences in neonates who progress to allergic disease in the first year of life.

Suppression of allergic inflammation by allergen-DNA-modified dendritic cells depends on the induction of Foxp3+ Regulatory T cells

CD4(+)CD25(+)Foxp3(+)Regulatory T cells (Tregs) play important roles in regulating allergic inflammation. To analyse if allergen-DNA-modified dendritic cells (DC) can suppress allergic responses and what roles Treg cells play in DC-based allergen-specific immunotherapy. Immature DC were transfected with retrovirus encoding Der p2 DNA, and administered to mice that sensitized and challenged with Der p2 protein. After Treg cells were depleted with anti-CD25 mAb, mice were re-challenged to observe the airway inflammation, and Treg cells in spleen CD4(+) T cells. And responses of spleen CD4(+) T cells to Der p2 were determined. Co-culture of naïve CD4(+) T cells with allergen-modified DC induced Foxp3+ Tregs. Sensitized and challenged mice developed allergic airway inflammation and Th2 responses, and decreased Foxp3(+) Tregs. Treatment with allergen-modified-DC suppressed airway inflammation and Th2 responses, and increased IL-10 and IFN-gamma production and Foxp3(+) Tregs significantly; and eliminated the responses of CD4(+) T cells to allergen. Administration of anit-CD25 mAb eliminated all the effects of modified-DC except for the increasing of IFN-gamma. Allergen-modified DC can induce immune tolerance to allergens and reverse the established Th2 responses induced by allergen, with dependence on the induction of Foxp3(+) Tregs.

Immune regulation by CD4+CD25+ T cells and interleukin-10 in birch pollen-allergic patients and non-allergic controls

BACKGROUND

CD4+CD25+ regulatory T (Treg) cells and the cytokines IL-10 or TGF-beta play key roles in the maintenance of T cell homeostasis and tolerance to infectious and non-infectious antigens such as allergens.

OBJECTIVE

To investigate the regulation of immune responses to birch pollen allergen compared with influenza antigen by Treg cells obtained from birch pollen-allergic patients and non-allergic controls.

METHODS

Peripheral blood was collected from 10 birch pollen-allergic patients and 10 non-allergic healthy controls. CD4+CD25+ and CD4+CD25- cells isolated by magnetic-activated cell sorting were co-cultured and stimulated with birch pollen extract or influenza vaccine in the absence or presence of anti-IL-10 or soluble TGF-betaRII.

RESULTS

CD4+CD25+ cells from non-allergic controls were able to suppress influenza antigen and birch pollen stimulated effector cell proliferation, whereas CD4+CD25+ cells from allergic patients suppressed influenza antigen-, but not birch pollen-stimulated proliferation. The production of Th1 cytokines, but not Th2 cytokines, was suppressed by CD4+CD25+ cells from both allergic patients and controls, upon stimulation with birch pollen extract. Neutralization of IL-10 led to significantly increased production of IFN-gamma in cultures with CD4+CD25- T effector cells. In addition, six-fold higher concentrations of TNF-alpha were detected after neutralization of IL-10 in both CD4+CD25- and CD4+CD25+ cell cultures from allergic patients and controls.

CONCLUSION

We demonstrate that the allergen-specific suppressive function of CD4+CD25+ cells from allergic patients is impaired compared with non-allergic controls. Moreover, neutralization of IL-10 enhances the production of TNF-alpha, suggesting counter-acting properties of IL-10 and TNF-alpha, where IL-10 promotes tolerance and suppression by Treg cells and TNF-alpha promotes inflammatory responses.

Regulatory T cells in allergy and asthma

Allergic diseases including asthma have risen considerably in prevalence in the last 50 years. A concomitant rise in autoimmune disease suggests a defect in immunoregulation, rather than a reduction in T-helper type 1 immunity. Immune responses to innocuous environmental antigens in health are characterized by dominant regulation through the production of interleukin-10 and transforming growth factor-beta. Recent studies suggest that diverse populations of regulatory T cells (Treg) play an important role in regulating T-helper type 2 (Th2) responses to allergens, maintaining functional tolerance. Regulatory responses appear to be compromised in allergic individuals but may be reconstituted to some extent with specific allergen immunotherapy. In experimental models, Treg can suppress Th2 responses to allergen, airway eosinophilia, mucous hypersecretion, and airway hyperresponsiveness. Further studies are required to precisely define the mechanisms of development and action of these cells, and to identify and evaluate novel targets for the treatment of allergic diseases.

Inhibition of human allergic T-helper type 2 immune responses by induced regulatory T cells requires the combination of interleukin-10-treated dendritic cells and transforming growth factor-beta for their induction

BACKGROUND

In grass pollen-allergic individuals, T cell anergy can be induced by IL-10-treated dendritic cells (IL-10-DC) resulting in the suppression of T helper type 1 (Th1) as well as Th2 cells. This study was performed to analyse whether such IL-10-DC-treated T cells are able to act as regulatory T cells (Treg) suppressing the function of other T cells in the periphery. As transforming growth factor (TGF)-beta is also a potential inducer of Treg, we additionally analysed the inhibitory capacity of TGF-beta-treated T cells in this system.

MATERIALS AND METHODS

Freshly isolated CD4+ or CD4+ CD25- T cells from grass pollen-allergic donors were stimulated with autologous mature monocyte-derived allergen-pulsed DC in the presence or absence of T cells previously cultured with IL-10-DC- and/or TGF-beta.

RESULTS

Anergic T cells induced by allergen-pulsed IL-10-treated DC or allergen-pulsed DC and TGF-beta enhanced IL-10 production and strongly inhibited IFN-gamma production of freshly prepared peripheral CD4+ or CD4+ CD25- T cells while proliferation and Th2 cytokine production were only slightly reduced. The combination of allergen-pulsed IL-10-treated DC and TGF-beta had an additional effect leading to a significant suppression also of Th2 cytokine production and proliferation. Suppression was not antigen-specific and was mainly mediated by cell-to-cell contact and by the molecule-programmed death-1 and only partially by CTLA-4, TGF-beta and IL-10.

CONCLUSION

These data demonstrate that regulatory T cells that also suppress Th2 cytokine production are induced by two signals: TGF-beta and IL-10-DC. This is of importance for the regulation of allergic immune responses and might be exploited for future therapeutic strategies for allergic diseases.

Demonstration of circulating allergen-specific CD4+CD25highFoxp3+ T-regulatory cells in both nonatopic and atopic individuals

BACKGROUND

CD4(+)CD25(+)Foxp3(+) T-regulatory (Treg) cells play a fundamental role in the control of autoimmunity. Whether human CD4(+)CD25(+)Foxp3(+) Treg cells that recognize foreign antigens also exist is less clear.

OBJECTIVE

To investigate the existence in humans of circulating Treg cells able to recognize exogenous antigens, including allergens.

METHODS

CD4(+)CD25(high)Foxp3(+) and CD4(+)CD25(-)Foxp3(-) cells were purified from human peripheral blood and cultured for 15 days with autologous dendritic cells (DCs), unloaded, or loaded with Der p 1 allergen or the bacterial antigen streptokinase (SK).

RESULTS

CD4(+)CD25(high)Foxp3(+) circulating T cells obtained from healthy nonatopic subjects and cultured with Der p 1-loaded DCs, but not those cultured with either unloaded or SK-loaded DCs, suppressed the proliferative response to Der p 1 of autologous Der p 1-specific T cells generated from the CD4(+)CD25(-)Foxp3(-) subset. The antigen specificity of either Der p 1-CD4(+)CD25(high)Foxp3(+) or SK-CD4(+)CD25(high)Foxp3(+) T cells was confirmed even at clonal level. Finally, under the same experimental conditions, functionally active Der p 1-specific Treg cells were obtained from the pool of circulating CD4(+)CD25(high)Foxp3(+) T cells of Der p 1-sensitive, atopic individuals.

CONCLUSION

These data provide undoubted demonstration of the existence of human CD4(+)CD25(high)Foxp3(+) circulating Treg cells specific for exogenous antigens, including the Der p 1 allergen, and indicate that CD4(+)CD25(high)Foxp3(+) Treg cells specific for Der p 1 are present and functionally active in both nonatopic and Der p 1-sensitive, atopic individuals.

CLINICAL IMPLICATIONS

Caution should be advised in interpreting allergic disorders as simply resulting from defective Treg cell activity.

Antibody blocking of MHC II on human activated regulatory T cells abrogates their suppressive potential

Natural regulatory CD4(+)CD25(+)Foxp3(+) T cells control peripheral immune responses. Freshly isolated regulatory T-cell populations are regarded as being unable to suppress the proliferation of strongly stimulated effector T cells. We now provide evidence that it is not the strength of the proliferative signal to effector T cells but activation and accessibility of regulatory T cells that determine whether suppression may occur. Human regulatory T cells were initially cocultured with allogeneic monocyte-derived dendritic cells for a short time and were then rendered accessible for effector T cells by removal of the dendritic cells. That way activated regulatory T cells effectively suppressed the proliferation of autologous effector T cells which was strongly driven by cell-sized Dynabeads coated with CD3/CD28 antibodies. Although regulatory T cells are known to display MHC II molecules and to upregulate their expression along with activation, a role of MHC II molecules in forming the contact to effector T cells was not yet envisaged. However, blocking of MHC II on activated regulatory T cells abrogated their suppressive potential. It should not be excluded that self-MHC molecules on physically accessible activated regulatory T cells arrange the contact to effector T cells.

The levels of CD4+CD25+ regulatory T cells in paediatric patients with allergic rhinitis and bronchial asthma

Our purpose was to determine whether numbers of CD4(+)CD25(+) T [T regulatory (T(reg))] cells and mRNA expression of functional molecules of T(reg) are related to airway allergy and disease severity in 51 paediatric patients with allergic rhinitis or bronchial asthma and 47 healthy controls. Surface markers were evaluated with flow cytometry, and mRNA was determined with real-time polymerase chain reaction. Children with allergic disease had fewer CD4(+)CD25(+) T cells (8 x 49% +/- 2 x 41% versus 9 x 58% +/- 2 x 43%, P<0 x 05) and CD4(+)CD25(hi) T cells (1 x 32% +/- 0 x 68% versus 1 x 70% +/- 0 x 68%, P<0 x 01) than control subjects. Numbers of CD4(+)CD25(+) and CD4(+)CD25(hi) T lymphocytes were higher in children with persistent allergic rhinitis and/or moderate-severe bronchial asthma than in those with respective milder disease. The number of T(reg) cells was correlated positively with total immunoglobulin E level. The mRNA expression of forkhead box P3 (FoxP3) was increased in moderate-severe versus mild asthma (2 x 93 +/- 0 x 38 versus 1 x 60 +/- 0 x 31, P< 0 x 01). Patients with moderate-severe bronchial asthma also had increased mRNA expression of interleukin (IL)-10 compared with patients with mild asthma (15 x 24 +/- 4 x 07 versus 3 x 77 +/- 2 x 18, P<0 x 01). The suppressive function of T(reg) cells from patients with more severe asthma was competent in vitro. On average, decreased numbers of T(reg) cells in children with allergic airway disease might represent a defect of the T(reg) population. With increased expression of FoxP3 and IL-10 in T(reg) from patients with relatively severe allergic disease, adaptive and functional T(reg) might be generated in response to aggravated atopy and disease severity.

A Possible Role of CD4+CD25+ T Cells as Well as Transcription Factor Foxp3 in the Dysregulation of Allergic Rhinitis

BACKGROUND

Allergic rhinitis (AR) is a Th2 predominant disease, and its pathogenic mechanism is still poorly understood. CD4(+)CD25(+) T cells account for approximately 5% to 10% peripheral CD4(+) T cells and has been shown to regulate the activation of effector T cells in the periphery. The activity of CD4(+)CD25(+) T cells is associated with the transcription factor Foxp3. The present study aimed to evaluate the possible role of CD4(+)CD25(+) T cells as well as Foxp3 in the pathogenesis of AR.

METHODS

Nasal tissues and peripheral blood mononuclear cells (PBMCs) were obtained from 17 patients with AR and 11 control subjects. Foxp3 was detected in nasal tissues by immunohistochemistry and real-time reverse transcription-polymerase chain reaction (RT-PCR). CD4(+)CD25(+) T cells and Foxp3 were evaluated in PBMCs by using flow cytometry. Concentrations of interleukin-2 (IL-2) and interferon-gamma (IFN-gamma) were measured by enzyme-linked immunosorbent assay (ELISA) in cultured PBMCs in the presence or absence of stimulation with phorbol ester (PMA) and Ionomycin.

RESULTS

The numbers of Foxp3(+) cells was 129.5 +/- 35.6 and 44.2 +/- 20.5 cells/mm(2) in nasal mucosa of two groups (P < .05). There were less Foxp3(+) lymphocytes and decreased Foxp3 mRNA in AR compared with the control (P < .05). The frequencies of the CD4(+)CD25(+) population in PBMCs of two groups were 1.99 +/- 0.95% and 3.55 +/- 1.27% (P < .05). There was significant difference in the frequencies of the Foxp3(+)CD4(+) CD25(+) population (1.81 +/- 0.77 vs 3.37 +/- 1.04, P < .05) and mean fluorescence intensity (MFI) of Foxp3 (5.93 +/- 2.64 vs 11.72 +/- 4.29, P < .05) in PBMCs of two groups. After stimulation, the concentrations of IL-2 and IFN-gamma were 182.72 +/- 85.11 pg/mL and 348.94 +/- 151.88 pg/mL in PBMCs with AR, while those were 90.6 +/- 61.5 pg/mL and 155.64 +/- 68.33 pg/mL in controls (P < .05).

CONCLUSION

Our results indicate that CD4(+) CD25(+) regulatory T cells as well as Foxp3 may play a crucial role in immunological imbalance of AR. These findings suggest that increasing Foxp3 and CD4(+)CD25(+) T cells have the potential to be new therapeutic targets for the treatment of AR.

[Mechanisms of specific immunotherapy]

Specific immunotherapy (SIT) is a well-established and clinically effective treatment for allergic rhinitis and bronchial asthma. The immunological mechanisms of the subcutaneously applied immunotherapy have been partially elucidated over the past several years but are not completely understood. This report summarizes the immunological and immunoregulatory changes during SIT of wasp venom allergic patients. The induction of IL-10-producing regulatory T cells is described.

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.