Recent Observations on the Heterogeneity of Human Effector Memory T Cells and Novel Cytokines Implicated in Cutaneous Inflammation and Psoriasis

Psoriasis is a chronic inflammatory skin disease that affects 2.2% of Americans and is a substantial detriment on the quality of life. Psoriasis is a complex interaction between numerous immune cells and has been considered largely a T-helper type 1 (Th1) T-cell-mediated response. Although numerous cytokines, including tumor necrosis factor-αβ, interleukin 1β, and interferon-γ, have been identified with distinct roles in skin inflammation and psoriasis, proinflammatory functions of newly identified cytokines have been linked recently to the alternative T-cell subsets Th17 and Th22 that are distinct in their functions and cytokine profiles. This review summarizes the basic research, translational applications, and new therapeutic developments contributing to the understanding of the diversity of human effector CD4+ Th1, Th17, and Th22 T cells, as well as the proinflammatory cytokines associated with these subsets in psoriasis.