Regulation of IgE Responses by γδ T Cells

Ex vivo assays show human gamma-delta T cells specific for common allergens are Th1-polarized in allergic donors

Gamma-delta (γδ) T cells contribute to the pathology of many immune-related diseases; however, no ex vivo assays to study their activities are currently available. Here, we established a methodology to characterize human allergen-reactive γδ T cells in peripheral blood using an activation-induced marker assay targeting upregulated 4-1BB and CD69 expression. Broad and reproducible ex vivo allergen-reactive γδ T cell responses were detected in donors sensitized to mouse, cockroach, house dust mite, and timothy grass, but the response did not differ from that in non-allergic participants. The reactivity to 4 different allergen extracts was readily detected in 54.2%-100% of allergic subjects in a donor- and allergen-specific pattern and was abrogated by T cell receptor (TCR) blocking. Analysis of CD40L upregulation and intracellular cytokine staining revealed a T helper type 1 (Th1)-polarized response against mouse and cockroach extract stimulation. These results support the existence of allergen-reactive γδ T cells and their potential use in rebalancing dysregulated Th2 responses in allergic diseases.

Integrative Transcriptomics Reveals Activation of Innate Immune Responses and Inhibition of Inflammation During Oral Immunotherapy for Egg Allergy in Children

We previously reported the results of a randomized, open-label trial of egg oral immunotherapy (OIT) in 50 children where 44% were desensitized and 46% were partially desensitized after 8 months of treatment. Here we focus on cell-mediated molecular mechanisms driving desensitization during egg OIT. We sought to determine whether changes in genome-wide gene expression in blood cells during egg OIT correlate with humoral responses and the clinical outcome. The blood cell transcriptome of 50 children receiving egg OIT was profiled using peripheral blood mononuclear cell (PBMC) samples obtained at baseline and after 3 and 8 months of OIT. We identified 467 differentially expressed genes (DEGs) after 3 or 8 months of egg OIT. At 8 months, 86% of the DEGs were downregulated and played a role in the signaling of TREM1, IL-6, and IL-17. In correlation analyses, Gal d 1–4-specific IgG4 antibodies associated positively with DEGs playing a role in pathogen recognition and antigen presentation and negatively with DEGs playing a role in the signaling of IL-10, IL-6, and IL-17. Desensitized and partially desensitized patients had differences in their antibody responses, and although most of the transcriptomic changes were shared, both groups had also specific patterns, which suggest slower changes in partially desensitized and activation of NK cells in the desensitized group. OIT for egg allergy in children inhibits inflammation and activates innate immune responses regardless of the clinical outcome at 8 months. Changes in gene expression patterns first appear as posttranslational protein modifications, followed by more sustained epigenetic gene regulatory functions related to successful desensitization.

Expression of CD27 and CD28 on γδ T cells from the peripheral blood of patients with allergic rhinitis

The costimulatory receptors CD27 and CD28 have pivotal and non-redundant roles in the activation and differentiation of γδ T-cells. However, the roles of CD27 and CD28 on γδ T-cells in allergic rhinitis (AR) have remained elusive. The aim of the present study was to investigate the expression of CD27 and CD28 on γδ T cells in patients with AR. Peripheral blood mononuclear cells from 14 patients with AR and 12 healthy subjects were isolated and analyzed by flow cytometry to determine the percentage of γδ T cells and regulatory T cells (Tregs), and the expression of IFN-γ, IL-17A, CD27 and CD28 on γδ T cells. The correlations between the expression of CD27 and CD28, and the percentages of IFN-γ+ and IL-17A+ γδ T-cell subsets and Tregs in AR were analyzed. It was observed that the percentages of γδ T cells, and the IL-17A+, CD27-CD28+ and CD27-CD28- γδ T-cell subsets were significantly increased, while the percentages of Tregs and IFN-γ+ and CD27+CD28+ γδ T-cell subsets were significantly decreased in AR. Of note, the percentage of CD27+CD28+ γδ T-cell subsets was positively correlated with that of the IFN-γ+ γδ T-cell subset and the percentage of the CD27-CD28+ γδ T-cell subset was positively correlated with that of the IL-17A+ γδ T-cell subset. Furthermore, the percentages of γδ T cells and the CD27-CD28+ γδ T-cell subset were both negatively correlated with that of Tregs. Therefore, the results of the present study indicate that CD27 and CD28 may be the key signals for activation of different γδ T-cell subsets and may contribute to the immune regulatory function of γδ T cells in the peripheral blood of patients with AR.

Characterization of the γδ T-cell compartment during infancy reveals clear differences between the early neonatal period and 2 years of age

γδ T cells are unconventional T cells that function on the border of innate and adaptive immunity. They are suggested to play important roles in neonatal and infant immunity, although their phenotype and function are not fully characterized in early childhood. We aimed to investigate γδ T cells in relation to age, prematurity and cytomegalovirus (CMV) infection. Therefore, we used flow cytometry to characterize the γδ T-cell compartment in cord blood and peripheral blood cells from 14-day-, 2-year- and 5-year-old children, as well as in peripheral blood samples collected at several time points during the first months of life from extremely premature neonates. γδ T cells were phenotypically similar at 2 and 5 years of age, whereas cord blood was divergent and showed close proximity to γδ T cells from 14-day-old neonates. Interestingly, 2-year-old children and adults showed comparable Vδ2+ γδ T-cell functionality toward both microbial and polyclonal stimulations. Importantly, extreme preterm birth compromised the frequencies of Vδ1+ cells and affected the functionality of Vδ2+ γδ T cells shortly after birth. In addition, CMV infection was associated with terminal differentiation of the Vδ1+ compartment at 2 years of age. Our results show an adult-like functionality of the γδ T-cell compartment already at 2 years of age. In addition, we demonstrate an altered γδ T-cell phenotype early after birth in extremely premature neonates, something which could possible contribute to the enhanced risk for infections in this vulnerable group of children.

Characterization of Mouse γδ T Cell Subsets in the Setting of Type-2 Immunity

Accumulating evidence indicates that γδ T cells are a critical component of type-2 immunity. However, the role of these cells in type-2 immune responses seems to be divergent. γδ T cells are heterogeneous lymphocytes that can be further divided into TCR-Vγ/δ definable subsets. Different subsets have distinct and sometimes opposite function during immune responses. In this chapter, we describe the detailed protocol for characterization of γδ T cell subsets in a mouse model of ovalbumin (OVA)/alum-induced type-2 immunity. Our protocol includes identifying γδ T cell subsets by flow cytometry, functionally inactivating individual subsets in vivo, purifying γδ T cell subsets, and using adoptive cell transfer to explore the role of individual subsets in OVA/alum-induced IgE responses.