Drug screening studies for inflammatory skin diseases are currently performed using model systems that only partially recapitulate human diseased skin. Here, we developed a new strategy to incorporate T cells into human 3D skin constructs (HSCs), which enabled us to closely monitor and quantitate T cell responses. We found that the epidermis promotes the activation and infiltration of T cells into the skin, and provides a directional cue for their selective migration towards the epidermis. We established a psoriatic HSC (pHSC) by incorporating polarized Th1/Th17 cells or CCR6+CLA+ T cells derived from psoriasis patients into the constructs. These pHSCs showed a psoriatic epidermal phenotype and characteristic cytokine profiles, and responded to various classes of psoriasis drugs, highlighting the potential utility of our model as a drug screening platform. Taken together, we developed an advanced immunocompetent 3D skin model to investigate epidermal-T cell interactions and to understand the pathophysiology of inflammatory skin diseases in a human-relevant and patient-specific context.Skin is equipped with a complex immune system that involves various immune cell types, such as T cells, Langerhans cells, dermal dendritic cells, mast cells, and basophils, which secrete cytokines and chemokines to regulate immune responses both locally and systemically. Perturbations in this complex regulatory mechanism due to genetic and/or environmental factors contribute to the development of inflammatory skin diseases 1 . Therefore, understanding the skin immune system is essential to investigate the pathogenesis of inflammatory skin diseases and to discover and validate effective targets for treatment.Psoriasis affects 2-3% of the Western population 2,3 and is a chronic inflammatory skin disease with dysregulated keratinocyte proliferation 4 . In the pathogenesis of psoriasis, the interplay between keratinocytes and immune cells is important for the initiation, progression and persistence of the disease. Psoriatic keratinocytes recruit and activate plasmacytoid dendritic cells and neutrophils to initiate psoriasis 5-8 , and produce autoantigens, such as LL37 5-7 , ADAMTSL5 9 , and PLA2G4D 10 to activate T cells. Once T cells and DCs are recruited and activated, a cytokine niche is established including IFNs, IL-17, TNFα, and IL-22 11-13 . These cytokines not only alter epidermal proliferation and differentiation 12,13 , but also activate keratinocytes to release chemokines and chemoattractants, which induce further recruitment and infiltration of inflammatory cells into the skin 11 . Although this complex feedback loop between keratinocytes and immune cells is central in the pathogenesis of psoriasis, current in vitro models do not capture these cellular interactions, such as migration of the immune cells, highlighting the need for an advanced model that recapitulates the physiological and immunological complexity of the disease.Although there have been improvements in the efficacy of biologic therapies, therapeutic outcomes v...
