Langerhans cells are a subtype of dendritic cells located in the epidermis of the skin and playing a major role in many inflammatory diseases. After antigen recognition and internalization, they migrate from the involved site to secondary lymph nodes to present the prepared antigen to naïve T cells. The aim of the present study was to quantify the effects of a Pickering emulsion combining an immunosuppressive drug, cyclosporin A or tacrolimus (Tac), encapsulated in PLGA nanoparticles, with an anti-inflammatory drug, calcitriol (Cal), contained in the dispersed phase on of Langerhans cells (LC). Emulsions were studied on epidermal LCs isolated either after topic application of emulsions on skin explants or direct incubation after isolation from healthy skin (n=6). An in vitro model of monocyte differentiation to LC (moLC) was also used for phenotyping moLCs in the presence of the emulsions. The antigenic presentation capacity (APC) of both skin LCs and moCLs was quantified in vitro using an allogenic mixed lymphocyte reaction (MLR). Our results demonstrate a significant decrease in lymphocyte proliferation in MLR with LCs either isolated after topic treatment of skin explants or isolated and then incubated with the emulsions. This was especially detected with the Tac/Cal combination. The phenotyping of moLCs showed that the expression of activation markers CD40, CD86 and HLA-DR was significantly decreased in the presence of the emulsions. Of interest, their APC was also significantly reduced in MLR. Altogether, our Pickering emulsions prove to be effective in modulating LC activity. The combination of these two drugs into a single formulation could be relevant for the treatment of inflammatory dermatoses where LCs are involved, notably psoriasis and atopic dermatitis.

ESDR238 - Modulation of the antigen presentation capacity of Langerhans cells by a Pickering emulsion combining an immunosuppressive and an anti-inflammatory drug

50th Annual Meeting of the European Society for Dermatological Research. VIRTUAL MEETING