Work

Seasonal changes in suppressive capacity of CD4+ CD25+ T cells from patients with hayfever are allergen‐specific and may result in part from expansion of effector T cells among the CD25+ population

Year: 2009

Type: article

Abstract: BACKGROUND: Suppression of allergen-stimulated peripheral blood CD4(+) CD25(-) effector T cells by CD4(+) CD25(+) regulatory T cells obtained from subjects with allergic rhinoconjunctivitis is reduced during the pollen season when compared with out of season. OBJECTIVE: We examined possible explanations for this effect of seasonal pollen exposure on suppression of allergen responses. METHODS: CD4(+) CD25(-) and CD4(+) CD25(+) T cells were isolated from blood obtained from 44 volunteers with allergic rhinoconjunctivitis during and out of the UK grass pollen season. Co-cultures were performed with grass pollen extract and house dust mite (HDM) to examine allergen specificity. The frequency of IL-5 and IL-10 producing cells was determined by ELISPOT and the expression of T cell activation markers and the CD25(+) regulatory T cell-associated transcription factor Foxp3 were examined. Lactic acid stripping of IgE was used to determine IgE dependence of T cell responses. RESULTS: The seasonal reduction in suppression by CD4(+) CD25(+) T cells was confirmed and was shown to be allergen specific because suppression of HDM-stimulated cultures was not affected significantly. The CD4(+) CD25(+) population contained IL-5 and IL-10 producing cells but increases in their frequencies with seasonal pollen exposure were not significant. Both activation marker and Foxp3 expression increased during the pollen season. IgE stripping reduced CD4(+) and CD4(+) CD25(-) T cell responses to allergen, but had no effect on suppression by CD4(+) CD25(+) T cells. CONCLUSION: The seasonal reduction in suppression of grass pollen-stimulated effector T cells by CD4(+) CD25(+) T cells is allergen specific and cannot be explained by increased IgE-facilitated allergen presentation. We suggest that changes in the proportion of effector to regulatory T cells among the CD25(+) population isolated may partially explain these findings, and that trafficking to the site of allergic disease may reduce allergen-specific regulatory T cell numbers in peripheral blood.

Source: Clinical & Experimental Allergy

DOI: 10.1111/j.1365-2222.2009.03320.x