The distinct role and regulatory mechanism of IL-17 and IFN-γ in the initiation and development of plaque vs guttate psoriasis

Background Few studies have explored the differences of immunopathogenesis in plaque vs guttate psoriasis, especially on the inhibitory role of regulatory T cells (Tregs) on IL-17/ IFN-γ production and the impact of CD4+T cells on keratinocytes. Objective To investigate the percentage and inhibitory function of CD4+CD25highTreg and differential expressions of IL-17/ IFN-γ in plaque vs guttate psoriasis, and the effects of CD4 + T cells on the proliferation of keratinocytes. Methods Peripheral blood mononuclear cells (PBMCs) were prepared from patients with the plaque and guttate psoriasis. The percentage of CD4+CD25high Tregs, IL-17/IFN-γ- producing CD4+ or CD8 + T cells, and apoptosis and cell cycle of Hacat cells were determined by flow cytometry. The level of IFN-γ in supernatants was analyzed by ELISA. Results The percentage of CD4+CD25highTregs in plaque psoriasis was significantly increased, and they can inhibit IFN-γ production from CD4+CD25- effector T cells. The percentage of CD8+IFN-γ+cells was also significantly increased in plaque psoriasis, and these cells positively correlated with disease severity. The percentage of CD4+CD25highTregs was decreased and CD4+IFN-γ+/IFN-γ+IL-17+ cells were predominantly increased in guttate psoriasis. CD4+T cells from guttate psoriasis induce apoptosis of keratinocytes while they promote the proliferation of keratinocytes in plaque psoriasis by decreasing late apoptosis and increasing the percentage of G1 phase. Conclusion There was considerable discrepancy of the phenotype and function of T cells between plaque vs guttate psoriasis. IFN-γ and IL-17 from CD4+T cells play a crucial role in guttate psoriasis, however, IFN-γ and IL-17 from CD8+T cells are more important in the immunopathogenesis of plaque psoriasis.