Lack of allergy to timothy grass pollen is not a passive phenomenon but associated with the allergen‐specific modulation of immune reactivity

Abstract

Background Timothy grass (TG) pollen is a common seasonal airborne allergen associated with symptoms ranging from mild rhinitis to severe asthma. Objective The aim of this study was to characterize changes in TG-specific T cell responses as a function of seasonality. Methods Peripheral blood mononuclear cells (PBMC) obtained from allergic individuals and non-allergic controls, either during the pollen season or out-of-season, were stimulated either with TG extract or a pool of previously identified immunodominant antigenic regions. Results PBMC from allergic subjects exhibit higher IL-5 and IL-10 responses in-season than when collected out of season. In the case of non-allergic subjects, as expected we observed lower IL-5 responses and robust production of IFNγ compared to allergic individuals. Strikingly, non-allergic donors exhibited an opposing pattern, with decreased immune reactivity in-season. The broad downregulation in non-allergic donors indicates that healthy individuals are not oblivious to allergen exposure but rather react with an active modulation of responses following the antigenic stimulus provided during the pollen season. Transcriptomic analysis of allergen-specific T cells defined genes modulated in concomitance with allergen exposure and inhibition of responses in non-allergic donors. Conclusion and Clinical Relevance Magnitude and functionality of T-helper cell responses differ substantially in-season versus out-of-season in allergic and non-allergic subjects. The results indicate specific and opposing modulation of immune responses following the antigenic stimulation during the pollen season. This seasonal modulation reflects the enactment of specific molecular programs associated with health and allergic disease.

Subcutaneous immunotherapy with purified Der p1 and 2 suppresses type 2 immunity in a murine asthma model

“…Specific immunotherapy (SIT) has been shown to induce durable immunological changes in response to the allergen, through generating neutralizing antibodies, through suppressing numbers and activity of allergen‐specific Th2 cells and type 2 innate lymphoid cells (ILC2s), and by inducing regulatory T‐cell activity 2. Successful SIT has been associated with enhanced release of IL‐10 in PBMC cultures restimulated with allergen,3 serum‐dependent suppression of cross‐presentation by B cells,4 and selective loss of those T‐cell clones with allergen‐epitope specificities that are increased in atopic individuals compared to healthy controls 5, 6. Specific immunotherapy (SIT) induces long‐term tolerance to the allergen, as evidenced by the absence of allergic manifestations upon repeated allergen challenges 1…”

Immunodominance in allergic T-cell reactivity to Japanese cedar in different geographic cohorts

“…Furthermore, studies on differences between immune recognition and responses of non-sensitized and sensitized donors in the JC system are extremely rare. Several reports suggest that non-sensitized individuals mount an immune response distinct from those of allergic individuals and are not oblivious to antigen stimulation 25–27 . Thus defining the features and targets of healthy individuals is important and understudied, and could provide insights for the development of safer and more efficacious immunotherapeutic approaches.…”

Strategies to Study T Cells and T Cell Targets in Allergic Disease

“…Another study, focused on Mugwort allergy, reported an ex vivo frequency of peptide-specific T cells of 0-0.029% in allergic cohort [34]. In a third study, performed with cells from patients allergic to Timothy grass, the authors reported epitope-specific T cell frequencies of 0.6-0.75% of the total CD4+ T cell subset [35], with a modest increase in frequencies detected during grass pollen season. The rarity of allergen-specific T cells poses a great challenge for epitope identification, as it will require the T cell reactivity assay to reliably detect a few single cells that respond to the peptide among several thousands of CD4+ T cells.…”

“…In vaccinology, tetramers are often used to track frequencies of peptide-specific T cells in the blood before and after vaccination or boost. Similarly, in allergy, tetramers have been used to quantify numbers of specific T cells as a variable of allergen season [35], allergen-specific immunotherapy [39], and disease status [34,40]. In addition, tetramer staining can be combined with other methodologies to perform more detailed immunological characterization of allergen-specific T cells.…”

“…If the antigen-specific T cell population is extremely rare, which is often the case in allergy and asthma, an enrichment step can be performed. To further enrich antigen-specific cells before flow cytometric analysis or isolation, microbeads conjugated to monoclonal antibodies specific for the respective fluorophore used in the experiment can be used to label cells, followed by magnetic column enrichment [35]. After cells are labeled and the enrichment step has been performed if desired, viable cells can be analyzed and isolated by flow cytometry, facilitating downstream applications, such as further culture assays or DNA/RNA extraction for sequencing analysis.…”