Memory IL-22-producing CD4+ T cells specific for Candida albicans are present in humans.

Co-expression of IL-22 and IL-17 has been identified and demonstrated to be involved in the immunopathogenesis of some autoimmune diseases as well as the defense against pathogenic infections in animal studies. However, the properties of IL-22-producing cells in humans remain largely unclear. In the present study, we showed that IL-22 could be induced from human PBMC following various polyclonal stimulations. The majority of IL-22-producing cells in PBMC were CD4(+) T cells with a memory cell phenotype. In addition, we found that a subset of IL-22(+) T cells produced IL-22 alone, whereas other IL-22(+) T cells co-expressed cytokines typical of Th1, Th2 and Th17 cells. Importantly, stimulation of PBMC from healthy adults with heat-inactivated Candida albicans (C. albicans) yeast or hyphae resulted in IL-22 production by central and effector memory CD4(+) T cells. Moreover, CD4(+)CCR6(+) but not CD4(+)CCR6(-) T cells produced IL-22 when stimulated with either C. albicans or PMA and ionomycin. In addition, PBMC from the individuals infected with C. albicans produced a significantly higher amount of IL-22 compared with healthy controls following stimulation with C. albicans. These data demonstrate that IL-22-producing T cells in humans may play an important role in the defense against fungal infections such as C. albicans.