Human keratinocytes and monocytes co-culture cell system: An important contribution for the study of moderate and weak sensitizers

In vitro approaches to address key events in chemical-induced skin sensitization have been developed, but there is still uncertain how they will be useful to predict the potency for an effective risk assessment. Keratinocytes (KCs) play a key role in all phases of skin sensitization. Dendritic cells (DCs) activation and maturation require the binding of cytokines produced by KC as a result of initial chemical exposure. We previously identified interleukin-18 (IL-18) as useful marker for determination of skin sensitization potential of chemicals. The aim of this paper was to mimic the interaction between KCs and DCs using a co-culture of NCTC 2544 and THP-1 cells. Three selected contact allergens of different potency (Bandrowski's base, diethyl maleate, and imidazolidinyl urea) were tested in time-course experiments (24, 48 and 72 h). Cell surface markers expression (CD80, CD86, and HLA-DR) was determined by flow cytometry analysis while IL-18 production was evaluated with specific sandwich ELISA. Results obtained from this simple in vitro co-culture system show the possibility to study the contribution of KCs in DCs activation through the analysis of HLA-DR expression. Results obtained demonstrate the ability of the KCs to favor the full maturation of the DCs in the presence of moderate and weak allergens, while the extreme allergen induced a complete maturation of DC alone without the need of KCs. •This paper describes the possible cross-talk between DCs and KCs (NCTC 2544) in ACD through a simple in vitro co-culture system.•The aim of this work was to better understand the in vitro behavior of moderate and weak sensitizers .•KCs favor the full maturation of the DCs in the presence of moderate and weak allergens