Abstract: Objective: To establish a method for detection of interleukin-22 producing cells in lymphocyte subpopulations from peripheral blood by flow cytometry.Methods: Peripheral blood samples were mixed with same volume of RPMI 1640 medium and stimulated with PMA and ionomycin for 6 hours in the presence of monensin at last 4 hours at 37℃,5% CO₂.The stimulated cells were stained for surface molecules or intracellular cytokines with fluorochrome-conjugated mAbs.The proportions of IL-22 producing cells and IL-17 producing cells among different lymphocyte subsets were detected by flow cytometry.Results: The proportions of IL-22 producing cells among CD3⁺T cells,CD4⁺T cells,CD8⁺T cells,NK cells and B lymphocytes were 1.83%,2.12%,0.67%,1.96% and 1.09%,respectively.The amount of IL-22 producing cells among CD4⁺T cells was significantly higher than that among CD8⁺T cells(P<0.01).In addition,IL-22 and IL-17 co-expressing cells were also detected in CD3⁺T cells,CD4⁺T cells,and CD8⁺T cells.Conclusions: By using flow cytometry technique,the IL-22 producing cells exist among all CD4⁺T cells,CD8⁺T cells,NK cells and B lymphocytes.The proportion of IL-22 producing cells in CD4⁺T cells is higher than that in CD8⁺T cells.