Van den Bogaard et al. reported that skin equivalents populated with activated CD4+ T cells or in vitro polarized Th1 and Th17 cells induced the expression of psoriasis-associated marker genes DEFB4, LCE3A, PI3, and KRT16 and elicited psoriasis-like epidermal inflammation (van den Bogaard et al., 2014). Here, CD4 is linked to psoriasis.