Aim: To determine subpopulations and cytokine expression of naïve and memory T cells by polychromatic flow cytometry(PFC).
Methods: PBMCs were separated from normal human peripheral blood and stimulated by superantigen (SEB). After incubation for 5 hours, the cells were fixed, permeablized and stained with multiplecolor-labeled mAbs for cell surface and intracellular cytokines. Then they were detected by polychromatic flow cytometry and the data were analyzed by Flow Jo software.
Results: Based on the expression of CD45RO molecules, CD4(+) and CD8(+) T cells were classified as naïve and memory cells, which were further devided into several subsets according to the expression of CD62L and CCR7. When PBMCs were stimulated by SEB for 5 hours, CD45RO(+) and CD45RO(-) CD4(+) or CD8(+) T cells expressed IL-2, IFN-gamma and TNF-alpha. Further analysis indicated that CD62L(lo) CCR7(lo) and CCR7(+) T cells but not CD62L(hi) and CD62L(hi) CCR7(+) T cells expressed cytokines. In addition, the percentage of cytokine expression in CD62L(lo) CCR7(lo) subsets was markedly higher than that in CCR7(+) subsets.
Conclusion: It is not scientific to identify naïve and memory cells in human T cells only based on the expression of CD45RO. Accurate determination of naïve, effector and memory cell populations can be achieved not only based on the expression of CD45RO but also according to the expression of CD62L.