Project description:Foxp3+ regulatory T cells (Treg) play a central role for tolerance against self and innocuous environmental antigens. However, the role of antigen-specificity for Treg-mediated tolerance is only incompletely understood. Here we show by direct ex vivo characterization of human CD4+ T cells, that the response against innocuous airborne antigens, such as plant pollen or fungal spores, is dominated by memory-like antigen-specific Treg. Surprisingly, breakdown of tolerance in atopic donors was not accompanied by a quantitatively or qualitatively altered Treg response, but instead correlated with a striking dichotomy of Treg versus Th2 target specificity. Allergenic proteins, are selectively targeted by Th2 cells, but not Treg. Thus human Treg specific for airborne antigens maintain tolerance at mucosal sites and the failure to generate specific Treg against a subgroup of antigens provides a window of opportunity for allergy development. PBMCs from sex and age matched birch pollen allergic patients and healthy controls, were stimulated (7h) with airborne fungal (A. fumigatus) or birch pollen antigen (birch) and sorted into antigen specific conventional and regulatory T cells according to their expression of CD154+ and CD137+ on CD4+ T cells, respectively. Number of samples per group in parentheses: Healthy controls stimulated with A. fumigatus (n=5), allergic patients stimulated with A. fumigatus (n=6), healthy controls stimulated with birch (n=6), allergic patients stimulated with birch (n=4).
