HDAC9 and psoriasis: Treg cells from psoriatic patients had enhanced propensity to differentiate to IL-17A-producing cells in cells stimulated ex vivo with IL-23 (cytokine strongly associated with the psoriasis, Figure 1, m), but, interestingly, the treatment with trichostatin-A, a “histone/protein deacetylase” (HDAC) inhibitor prevented the cellular differentiation [130].