A novel, dual cytokine-secretion assay for the purification of human Th22 cells that do not co-produce IL-17A.

BACKGROUND: Interleukin-22 is produced by certain T helper cells subsets (Th17, Th22) and at lower levels by γ-δ T cells, NKT and innate lymphoid cells. Th22 cells are unique immune cells that regulate tissue responses by IL-22 production. The exact discrimination between Th17 cells that co-produce IL-22 and single IL-22-producing Th22 cells has not been possible until the present study. Isolation of pure Th22 cells without co-expression of cytokines of other T-cell subsets is essential to better understand their function in humans. The aim of this study is the isolation and characterization of viable, human IL-22-producing CD4+ T cells that do not produce IL-17A.
METHODS: Isolation of viable Th22 cells was performed with the combination of two cytokine secretion assays detecting IL-17A- and IL-22-producing cells in a single purification step.
RESULTS: The newly developed cytokine secretion assay consists of anti-IL-22 and anti-IL-17A catch antibodies, which via biotin-streptavidin interaction are bound to the biotinylated surface of the target cell, and anti-IL-22 and IL-17A detection antibody labelled with a fluorescent dye, which detects cytokines bound to these catch antibodies. A unique population of human Th22 cells, which do not produce IL-17A, was sorted, and cytokine expression pattern was confirmed by quantitative PCR analysis and ELISA. The presented technique allows the detection and isolation of pure human Th22 cells.
CONCLUSIONS: This technique may allow the purification of any single cytokine-producing cell subset, and the combination of several different cytokine secretion assays can be used to purify and characterize novel and unique cell subsets.