Detection of antigen-specific T cells based on intracellular cytokine staining using flow-cytometry.

CMV-specific T cells may be detected and quantified after antigen-specific stimulation based on the induction of cytokines as a readout system. Secreted cytokines may be detected from the supernatant of stimulated cells using ELISA. Alternatively, antigen-specific cytokine-secreting cells may be enumerated using an ELISPOT assay. These assays generally rely on the detection of IFNγ and do not allow for a simultaneous assessment of several cytokines on a single cell basis. Here we describe a flow-cytometry based method to analyze CMV-specific CD4 T cells after specific stimulation with a whole antigen lysate. In this assay, cytokine secretion from stimulated cells is blocked by the addition of brefeldin A. Using a panel of fluorescently labeled antibodies, not only intracellularly accumulated cytokines but also phenotypical characteristics of specifically activated T cells may be quantified in a multiparameter staining approach.