Chemokine receptor expression on allergen-specific T cells in asthma and allergic bronchopulmonary aspergillosis

Current and future biomarkers in allergic asthma

Diagnosis early in life, sensitization, asthma endotypes, monitoring of disease and treatment progression are key motivations for the exploration of biomarkers for allergic rhinitis and allergic asthma. The number of genes related to allergic rhinitis and allergic asthma increases steadily; however, prognostic genes have not yet entered clinical application. We hypothesize that the combination of multiple genes may generate biomarkers with prognostic potential. The current review attempts to group more than 161 different potential biomarkers involved in respiratory inflammation to pave the way for future classifiers. The potential biomarkers are categorized into either epithelial or infiltrate-derived or mixed origin, epithelial biomarkers. Furthermore, surface markers were grouped into cell-type-specific categories. The current literature provides multiple biomarkers for potential asthma endotypes that are related to T-cell phenotypes such as Th1, Th2, Th9, Th17, Th22 and Tregs and their lead cytokines. Eosinophilic and neutrophilic asthma endotypes are also classified by epithelium-derived CCL-26 and osteopontin, respectively. There are currently about 20 epithelium-derived biomarkers exclusively derived from epithelium, which are likely to innovate biomarker panels as they are easy to sample. This article systematically reviews and categorizes genes and collects current evidence that may promote these biomarkers to become part of allergic rhinitis or allergic asthma classifiers with high prognostic value.

Abnormal chemokine receptor profile on circulating T lymphocytes from nonallergic asthma patients

BACKGROUND

T lymphocytes are involved in the pathogenesis of nonallergic asthma. The objective of this study was to characterize the subset distribution and pattern of chemokine receptor expression in circulating T lymphocyte subsets from nonallergic asthma patients.

METHODS

Forty stable nonallergic asthma patients and 16 sex- and age-matched healthy donors were studied. Twelve patients did not receive inhaled steroids (untreated patients), 16 received 50-500 μg b.i.d. of inhaled fluticasone propionate (FP) (standard-dose patients), and 12 received over 500 μg b.i.d. of inhaled FP (high-dose patients) for at least 12 months prior to the beginning of this study and were clinically well controlled. Flow cytometry was performed using a panel of monoclonal antibodies (4 colors).

RESULTS

Nonallergic asthma patients treated with high doses of inhaled FP showed a significant reduction in the percentages of CD3+ T lymphocytes compared to healthy controls. Untreated patients showed a significant increase in CCR6 expression in CD8+CD25+ and CD8+CD25+bright T cells compared to healthy controls. The results were similar for CXCR3 and CCR5 expression. In patients treated with standard doses of FP, CCR5 expression was significantly increased in CD3+ T lymphocytes relative to healthy controls.

CONCLUSIONS

The different groups of clinically stable nonallergic asthmatic patients showed distinct patterns of alterations in subset distribution as well as CCR6, CXCR3, and CCR5 expression on circulating T lymphocytes. .

Peanut oral immunotherapy results in increased antigen-induced regulatory T-cell function and hypomethylation of forkhead box protein 3 (FOXP3)

BACKGROUND

The mechanisms contributing to clinical immune tolerance remain incompletely understood. This study provides evidence for specific immune mechanisms that are associated with a model of operationally defined clinical tolerance.

OBJECTIVE

Our overall objective was to study laboratory changes associated with clinical immune tolerance in antigen-induced T cells, basophils, and antibodies in subjects undergoing oral immunotherapy (OIT) for peanut allergy.

METHODS

In a phase 1 single-site study, we studied participants (n = 23) undergoing peanut OIT and compared them with age-matched allergic control subjects (n = 20) undergoing standard of care (abstaining from peanut) for 24 months. Participants were operationally defined as clinically immune tolerant (IT) if they had no detectable allergic reactions to a peanut oral food challenge after 3 months of therapy withdrawal (IT, n = 7), whereas those who had an allergic reaction were categorized as nontolerant (NT; n = 13).

RESULTS

Antibody and basophil activation measurements did not statistically differentiate between NT versus IT participants. However, T-cell function and demethylation of forkhead box protein 3 (FOXP3) CpG sites in antigen-induced regulatory T cells were significantly different between IT versus NT participants. When IT participants were withdrawn from peanut therapy for an additional 3 months (total of 6 months), only 3 participants remained classified as IT participants, and 4 participants regained sensitivity along with increased methylation of FOXP3 CpG sites in antigen-induced regulatory T cells.

CONCLUSION

In summary, modifications at the DNA level of antigen-induced T-cell subsets might be predictive of a state of operationally defined clinical immune tolerance during peanut OIT.

Epigenetically mediated pathogenic effects of phenanthrene on regulatory T cells

Phenanthrene (Phe), a polycyclic aromatic hydrocarbon (PAH), is a major constituent of urban air pollution. There have been conflicting results regarding the role of other AhR ligands 2,3,7,8- tetrachlorodibenzo-p-dioxin (TCDD) and 6-formylindolo [3,2-b]carbazole (FICZ) in modifying regulatory T cell populations (Treg) or T helper (Th)17 differentiation, and the effects of Phe have been understudied. We hypothesized that different chemical entities of PAH induce Treg to become either Th2 or Th17 effector T cells through epigenetic modification of FOXP3. To determine specific effects on T cell populations by phenanthrene, primary human Treg were treated with Phe, TCDD, or FICZ and assessed for function, gene expression, and phenotype. Methylation of CpG sites within the FOXP3 locus reduced FOXP3 expression, leading to impaired Treg function and conversion of Treg into a CD4⁺CD25^lo Th2 phenotype in Phe-treated cells. Conversely, TCDD treatment led to epigenetic modification of IL-17A and conversion of Treg to Th17 T cells. These findings present a mechanism by which exposure to AhR-ligands mediates human T cell responses and begins to elucidate the relationship between environmental exposures, immune modulation, and initiation of human disease.

A novel mechanism of soluble HLA-G mediated immune modulation: downregulation of T cell chemokine receptor expression and impairment of chemotaxis

Background

In recent years, many immunoregulatory functions have been ascribed to soluble HLA-G (sHLA-G). Since chemotaxis is crucial for an efficient immune response, we have investigated for the first time the effects of sHLA-G on chemokine receptor expression and function in different human T cell populations.

Methodology/Principal Findings

T cell populations isolated from peripheral blood were stimulated in the presence or absence of sHLA-G. Chemokine receptors expression was evaluated by flow cytometry. sHLA-G downregulated expression of i) CCR2, CXCR3 and CXCR5 in CD4⁺ T cells, ii) CXCR3 in CD8⁺ T cells, iii) CXCR3 in Th1 clones iv) CXCR3 in TCR Vδ2γ9 T cells, and upregulated CXCR4 expression in TCR Vδ2γ9 T cells. sHLA-G inhibited in vitro chemotaxis of i) CD4⁺ T cells towards CCL2, CCL8, CXCL10 and CXCL11, ii) CD8⁺ T cells towards CXCL10 and CXCL11, iii) Th1 clones towards CXCL10, and iv) TCR Vδ2γ9 T cells towards CXCL10 and CXCL11. Downregulation of CXCR3 expression on CD4+ T cells by sHLA-G was partially reverted by adding a blocking antibody against ILT2/CD85j, a receptor for sHLA-G, suggesting that sHLA-G downregulated chemokine receptor expression mainly through the interaction with ILT2/CD85j. Follicular helper T cells (T_FH) were isolated from human tonsils and stimulated as described above. sHLA-G impaired CXCR5 expression in T_FH and chemotaxis of the latter cells towards CXCL13. Moreover, sHLA-G expression was detected in tonsils by immunohistochemistry, suggesting a role of sHLA-G in local control of T_FH cell chemotaxis. Intracellular pathways were investigated by Western Blot analysis on total extracts from CD4+ T cells. Phosphorylation of Stat5, p70 s6k, β-arrestin and SHP2 was modulated by sHLA-G treatment.

Conclusions/Significance

Our data demonstrated that sHLA-G impairs expression and functionality of different chemokine receptors in T cells. These findings delineate a novel mechanism whereby sHLA-G modulates T cell recruitment in physiological and pathological conditions.

[Refractory asthma: diagnosing allergic bronchopulmonary aspergillosis]

Allergic bronchopulmonary aspergillosis (ABPA) results from a twofold mechanism: Th2-like hypersensitivity reaction and bronchial colonization by Aspergillus fumigatus. This relatively rare disease occurs in immunocompetent patients in two very different situations: refractory asthma and cystic fibrosis. Diagnosis in asthma patients is relatively easy; it is based on the association of several criteria: clinical (recurrent exacerbations despite adequate therapy and a positive A. fumigatus skin prick-test), laboratory (inconsistent blood eosinophilia, high serum levels of total IgE, presence of A. fumigatus-specific IgE and IgG) and radiological (mainly central bronchiectasis, sometimes transitory pulmonary infiltrates). Diagnosis is more difficult in patients with cystic fibrosis because of the similarity of their various criteria. Long-term prognosis is good in the early stages of the illness, although the natural history and course of the disease are not fully understood. Early diagnosis and active screening for exacerbations are recommended to prevent bronchiectasis and progression to end-stage lung disease. Two drugs have shown their efficacy in treating ABPA: corticosteroids and itraconazole. They are recommended in acute exacerbations and should not be used as long-term therapy, except in corticosteroid-dependent asthma and in some cases of cystic fibrosis.