CD154 is a T cell activation marker, transiently expressed following ligation of the T cell receptor, therefore providing direct access to an antigen-specific T cell population. Using peripheral blood samples taken from allergic individuals and healthy non-atopic controls, this project identified and phenotyped CD154+ T helper cells following ex vivo stimulation with native allergen extracts (birch pollen, cat dander, grass pollen). Peripheral blood mononuclear cells were stimulated with allergen extract for 16 hours in the presence of Brefeldin A. Responding CD154+ T cells were identified and phenotyped using multiparametric flow cytometry. Activated CD154+ TH1, TH2 and TR1-like cells, that co-expressed IFNγ, IL4 and IL10 respectively, were identified in allergic and non-allergic participants. A close correlation was observed between TH1, TH2 and TR1-like cell frequency in non-allergic participants, such that the three parameters increased together to maintain a low TH2:TH1 ratio. The relationship between TH1, TH2 and TR1-like responses was dysregulated in allergic individuals, with abrogation of the IL10 response and a higher TH2:TH1 ratio. A close correlation was observed between Th2 cell frequency and the absolute concentration of birch-specific IgE. This work confirms previous reports of a more differentiated T cell phenotype in allergic subjects with regard to seasonal allergens. The detection of CD154+ T cells after short-term antigen stimulation may be a useful method for the detection of T cell responses to allergens when cost, speed and convenience are priorities.
|Date of Award||2012|