ENUMERATION OF IFN-GAMMA PRODUCING LYMPHOCYTES BY FLOW-CYTOMETRY AND CORRELATION WITH QUANTITATIVE MEASUREMENT OF IFN-GAMMA

We describe a flow cytometry method to simultaneously analyze IFN-gamm a production and T cell surface phenotype in freshly isolated lymphocy tes without requiring prior in vitro stimulation. We show that enumera tion of intracytoplasmic IFN-gamma positive T cells correlates with qu antitative measurement of IFN-gamma in culture supernatant fluids. Thi s suggests that cytokines can be reliably measured using flow cytometr y. Flow cytometry has the added advantage of simultaneous detection of cell surface markers. Furthermore, we suggest that analysis of ex viv o IFN-gamma production at the single cell level may reflect more accur ately T cell IFN-gamma production, by avoiding the polyclonal stimulat ion of IFN-gamma production observed after short term in vitro stimula tion.