Regulation of the Immune Cell Repertoire in Psoriasis Patients Upon Blockade of IL-17A or TNFα

Targeting of the pro-inflammatory cytokines interleukin 17A (IL-17A) or tumor necrosis factor alpha (TNFα) with monoclonal antibodies (mAbs) ixekizumab or adalimumab, respectively, are successful therapies in chronic plaque psoriasis. The effects of these treatments on immune cell populations in the skin are largely unknown. In this study, we compared the composition of cutaneous, lesional as well as non-lesional, and blood immune cells in ixekizumab or adalimumab treated patients with psoriasis. Our data reveal that both treatments efficiently down-regulate T-cells, macrophages and different subsets of dendritic cells (DCs) in lesional skin towards levels of healthy skin. In contrast to lesional skin, non-lesional areas in patients harbor only few or no detectable DCs compared to skin of healthy subjects. Neither the treatment with ixekizumab nor adalimumab reverted this DC imbalance in non-lesonal skin of psoriatic patients. Taken together, our study shows that anti-IL-17A as well as anti-TNFα therapy rebalances the immune cell repertoire of lesional skin in psoriatic patients, but fail to restore the disturbed immune cell repertoire in non-lesional skin during the induction phase of therapy.