An imbalance between frequency of CD4+CD25+FOXP3+ regulatory T cells and CCR4+ and CCR9+ circulating helper T cells is associated with active perennial allergic conjunctivitis

Immune regulation of the ocular surface

Despite constant exposure to various environmental stimuli, the ocular surface remains intact and uninflamed while maintaining the transparency of the cornea and its visual function. This 'immune privilege' of the ocular surface is not simply a result of the physical barrier function of the mucosal lining but, more importantly, is actively maintained through a variety of immunoregulatory mechanisms that prevent the disruption of immune homeostasis. In this review, we focus on essential molecular and cellular players that promote immune quiescence in steady-state conditions and suppress inflammation in disease-states. Specifically, we examine the interactions between the ocular surface and its local draining lymphoid compartment, by encompassing the corneal epithelium, corneal nerves and cornea-resident myeloid cells, conjunctival goblet cells, and regulatory T cells (Treg) in the context of ocular surface autoimmune inflammation (dry eye disease) and alloimmunity (corneal transplantation). A better understanding of the immunoregulatory mechanisms will facilitate the development of novel, targeted immunomodulatory strategies for a broad range of ocular surface inflammatory disorders.

Increased Expression of TLR4 in Circulating CD4+T Cells in Patients with Allergic Conjunctivitis and In Vitro Attenuation of Th2 Inflammatory Response by Alpha-MSH

Ocular allergic diseases are frequently seen in ophthalmological clinical practice. Immunological damage is mediated by a local Th2 inflammatory microenvironment, accompanied by changes in circulating cell subsets, with more effector cells and fewer T regulatory cells (Tregs). This study aimed to evaluate the involvement of toll-like receptor 4 (TLR4) and α-melanocyte stimulating hormone (α-MSH) in the immune regulation associated with perennial allergic conjunctivitis (PAC). We performed an Ag-specific stimulation during 72 h of culturing with or without lipopolysaccharide (LPS) or α-MSH in peripheral blood mononuclear cells (PBMC), analyzing the cell subsets and cytokines induced by the stimuli. We also determined α-MSH in tear samples from healthy donors (HD) or PAC patients. Our findings demonstrate an immunological dysregulation characterized by an increased frequency of CD4+TLR4+ in the PBMC of patients with PAC, compared to HD. Most of these CD4+TLR4+ cells were also CD25+, and when α-MSH was added to the culture, the percentage of CD4+CD25+FoxP3+ increased significantly, while the percentage of CD69+ cells and cytokines IL-4 and IL-6 were significantly decreased. In tears, we found an increased concentration of α-MSH in PAC patients, compared with HD. These findings indicate a novel mechanism involved in controlling ocular allergic diseases, in which α-MSH diminishes the concentration of IL-6 and IL-4, restoring the frequency of Tregs and down-regulating CD4 activation. Moreover, we demonstrated the involvement of CD4+TLR4+ cells as an effector cell subset in ocular allergy.

Low Expression of IL-10 in Circulating Bregs and Inverted IL-10/TNF-α Ratio in Tears of Patients with Perennial Allergic Conjunctivitis: A Preliminary Study

Allergic conjunctivitis (AC) is one of the most common ophthalmological disorders seen in clinical practice. Growing evidence from recent years suggests that a subset of IL-10-expressing B cells is involved in inflammatory allergic diseases. In this study, we aimed to evaluate the potential involvement of blood Bregs cells in perennial allergic conjunctivitis (PAC), and interleukins (IL)-1β, IL-6, IL-8, IL-10, and IL-12, and tumor necrosis factor (TNF)-α, were measured in tear samples and compared with healthy controls (HC) using flow cytometry. Non-significant differences in CD19⁺IL-10⁺ cell frequency between PAC patients and healthy controls (HC) were observed. Nevertheless, when we analyzed the mean fluorescence intensity (MFI) of IL-10 on CD19⁺CD38^Lo/Med/Hi-gated cells, we observed a significant decrease in MFI in all Bregs subsets in PAC patients. Additionally, tear cytokines showed 2.8 times lower levels of IL-10 than TNF-α in PAC patients when compared to HC. Our findings demonstrate an immunological dysregulation in patients with allergic conjunctivitis, characterized by the low expression of IL-10 in circulating CD19⁺CD38⁺ Bregs subsets and an inverted tear IL-10/TNF-α ratio, promoting a local pro-inflammatory microenvironment. These findings highlight the novel pathologic changes involved in ocular allergic diseases. Understanding systemic and local mechanisms will aid the design of immunomodulating therapeutics at different levels.

Food allergen-sensitized CCR9+ lymphocytes enhance airways allergic inflammation in mice

BACKGROUND

The mechanisms of the atopic march, characterized by a natural progression from food and cutaneous allergies to rhinitis and asthma, are still unknown. However, as several organs can be involved, chemokines and their receptors might be implicated in this process and may be instrumental factors.

OBJECTIVES

We hypothesized that the T-cell gut-homing receptor CCR9 could be implicated in the evolution of allergic diseases.

METHODS

We characterized the immune response and the role of CCR9 in a murine model combining food allergy to wheat gliadin and a model of acute airways inflammation in response to house dust mite.

RESULTS

Compared with solely asthmatic-like mice, we demonstrated that the aggravation of pulmonary symptoms in consecutive food and respiratory allergies, characterized by an increase in pulmonary resistance and a higher Th17/Treg ratio, was abrogated in CCR9 knockout mice. Moreover, transfer of food-allergic CD4⁺ T cells from wild-type but not from CCR9^-/- aggravated airways inflammation demonstrating that CCR9 is involved in food allergy-enhanced allergic airway inflammation to unrelated allergens.

CONCLUSION

Taken together, our results demonstrated a crucial role of the T-cell homing receptor CCR9 in this model and validated its potential for use in the development of therapeutic strategies for allergic diseases.

Conjunctival transcriptome profiling of Solomon Islanders with active trachoma in the absence of Chlamydia trachomatis infection

BACKGROUND

Clinical signs of active (inflammatory) trachoma are found in many children in the Solomon Islands, but the majority of these individuals have no serological evidence of previous infection with Chlamydia trachomatis. In Temotu and Rennell and Bellona provinces, ocular infections with C. trachomatis were seldom detected among children with active trachoma; a similar lack of association was seen between active trachoma and other common bacterial and viral causes of follicular conjunctivitis. Here, we set out to characterise patterns of gene expression at the conjunctivae of children in these provinces with and without clinical signs of trachomatous inflammation-follicular (TF) and C. trachomatis infection.

METHODS

Purified RNA from children with and without active trachoma was run on Affymetrix GeneChip Human Transcriptome Array 2.0 microarrays. Profiles were compared between individuals with ocular C. trachomatis infection and TF (group DI; n = 6), individuals with TF but no C. trachomatis infection (group D; n = 7), and individuals without TF or C. trachomatis infection (group N; n = 7). Differential gene expression and gene set enrichment for pathway membership were assessed.

RESULTS

Conjunctival gene expression profiles were more similar within-group than between-group. Principal components analysis indicated that the first and second principal components combined explained almost 50% of the variance in the dataset. When comparing the DI group to the N group, genes involved in T-cell proliferation, B-cell signalling and CD8+ T cell signalling pathways were differentially regulated. When comparing the DI group to the D group, CD8+ T-cell regulation, interferon-gamma and IL17 production pathways were enriched. Genes involved in RNA transcription and translation pathways were upregulated when comparing the D group to the N group.

CONCLUSIONS

Gene expression profiles in children in the Solomon Islands indicate immune responses consistent with bacterial infection when TF and C. trachomatis infection are concurrent. The transcriptomes of children with TF but without identified infection were not consistent with allergic or viral conjunctivitis.

Risk of allergic conjunctivitis in patients with type 1 diabetes mellitus: a population-based retrospective cohort study

OBJECTIVE

In accordance with the dichotomy between T helper type 1(Th1) and T helper type 2 (Th2) responses, the occurrence of allergic conjunctivitis (AC) and type 1 diabetes mellitus (T1DM) is, in theory, inversely related in the individual. However, recent studies investigating the association between the two diseases are controversial.

DESIGN

Population-based cohort study.

SETTING

We used claims data of the National Health Insurance Research Database of Taiwan.

PARTICIPANTS

We identified 4160 patients aged 1-30 years with newly diagnosed T1DM and no history of AC at baseline. For each patient with T1DM, four non-T1DM controls (n=16,640) were matched by sex. The mean follow-up time was 6 years.

PRIMARY AND SECONDARY OUTCOME MEASURES

Multivariate Cox proportional hazards regression analysis was used to evaluate the risk of AC. We additionally evaluated the association between risk of AC and T1DM progression by examining Diabetes Complications Severity Index (aDCSI) changes from the date of diagnosis until the end of follow-up.

RESULTS

The overall incidence of allergic conjunctivitis (AC) was higher in the type 1 diabetes mellitus (T1DM) cohort than in the control cohort (23.0 vs 13.5 per 1000 person-years, adjusted incidence rate ratio (aIRR): 1.59, 95% CI 1.47 to 1.71). Relative to that in patients with mildly progressive T1DM, the risk of AC increased as the adapted Diabetes Complications Severity Index (aDCSI) increased (aIRR: 1.68, 3.78 and 18.8, with yearly changes in aDCSI score: 0.51 to 1.00, 1.01 to 2.00, and >2.00 vs <0.51, respectively; for trend <0.001).

CONCLUSION

Patients with T1DM are at an elevated risk of developing AC; this risk increases with T1DM progression. The T helper type 1/T helper type 2 hypothesis is an overly simplistic explanation for this association.

Increased red cell distribution width levels in children with seasonal allergic conjunctivitis

PURPOSE

Seasonal allergic conjunctivitis (SAC) is an inflammatory disease of the conjunctiva. Red cell distribution width (RDW) is a widely accepted inflammatory marker. We aimed to investigate whether RDW level is associated with the development of SAC in pediatric population.

METHODS

The present study consisted of 90 subjects (45 children with SAC and 45 age- and sex-matched healthy children). The demographic findings, complete blood count parameters including RDW and laboratory parameters, were evaluated.

RESULTS

The mean RDW levels were significantly higher in children with SAC compared to the control group (14.02 ± 0.82 vs. 13.26 ± 0.64%, respectively, p < 0.001). In receiver operating characteristic analysis, the area under the curve for RDW for predicting SAC was 0.786, and a RDW value of 13.45 or higher predicted SAC with a sensitivity of 75.6% and specificity of 65%.

CONCLUSION

Our study suggests that elevated RDW levels are significantly associated with SAC in pediatric population, which may imply a possible role of increased inflammatory status and oxidative stress in the pathogenesis of SAC.

T helper subsets in allergic eye disease

PURPOSE OF REVIEW

Ocular allergy is an IgE-mediated disease that results in inflammation of the conjunctiva and, in more severe cases, the cornea. This is driven by an immediate hypersensitivity response via mast cells, followed by a late phase response mediated by eosinophils both of which are indeed dependent on T helper (Th) lymphocyte activity. Here, we provide an update on Th subsets [Th1, Th2, Th17, and T regulatory (Treg)] and their relevance in ocular allergy.

RECENT FINDINGS

Recent evidence in ocular allergy points to an involvement of other Th subsets, in addition to Th2. However, how these subsets are activated and their role in mediating the different clinical forms is poorly understood. Novel mouse models may facilitate addressing such unknowns, and future challenges will involve how to translate such findings into more effective and 'patho-specific' treatments.

SUMMARY

Ocular allergy, especially in severe forms, involves subsets other than Th2. Th1 cells have been detected in mild and severe forms, and recent evidence points to a possible role for IL-17 in severe disease. Tregs, on the other hand, dampen pathogenic Th cell function and allergy immunotherapy is associated with Treg augmentation in disease management. Further understanding of Th biology is warranted and may lead to better therapies.