[Characterization of memory CD4+ IL-21+ T cells in human PBMC]

To characterize IL-21-producing T cells in human PBMCs.

PBMCs from healthy individuals were stimulated with or without anti-CD3 (OKT3), OKT3 coupled with anti-CD28, or PMA coupled with ionomycin. The cell subsets of IL-21-producing T cells were determined by FACS. PBMCs, CD4+, CD4+CD45RA⁻, CD4+ CD45RA+ or CBMCs were stimulated with PMA coupled with ionomycin. The phenotype of CD4+ IL-21+ T cells and the correlation of IL-21-producing CD4+; T cells with Th1, Th2, Th17 and Th22 cell populations were analyzed by FACS.

PMA and ionomycin induced the highest level of IL-21 production among the stimuli tested. CD4+ T cells but not CD8+ T cells mainly expressed IL-21. CD4+ IL-21+ T cells expressed CD45RO instead of CD45RA. Some of the CD4+ IL-21+ T cells expressed CCR6, CCR7 or CXCR5. CD4+ CD45RA⁻ T cells expressed much more IL-21 than CD4+ CD45RA+ T cells. Furthermore, CD4+ T cells from PBMCs but not CBMCs, expressed IL-21. Approximately 24% of CD4+ IL-21+ cells expressed IFN-γ. Less than 10% of CD4+ IL-21+ cells expressed IL-4, IL-17 or IL-22.

IL-21 is induced from human PBMCs following various polyclonal stimulations. The majority of IL-21-producing cells in PBMCs are memory CD4+ T cells. In addition, some of the CD4+ IL-21+ T cells are distinct from Th1, Th2 and Th17 cells.