IL-17E, iNOS and Arginase1 as new biomarkers in the identification of neutrophilic dermatoses

BACKGROUND Neutrophilic dermatoses (ND) are a heterogenous group of diseases with often relatively similar histological appearance. OBJECTIVES The aim of this study is to identify a combination of biomarkers allowing a better differentiation of ND. METHODS Biopsies were obtained from normal human skin (NS, n=4), chronic plaque-type psoriasis (PSO, n=7), paradoxical psoriasis (PP, n=8), generalized pustular psoriasis (GPP, n=9), subcorneal pustular dermatosis of Sneddon-Wilkinson (SPD, n=3), acute generalized exanthematous pustulosis (AGEP, n=3), hidradenitis suppurativa (HS, n=7), Sweet syndrome (SS, n=8), and pyoderma gangraenosum (PG, n=8). Samples were analysed by immunofluorescence using 3 biomarkers, IL-17E, iNOS and Arginase1, each one in combination with 2 cell markers, MPO and CD68, which allow the identification of neutrophils and macrophages, respectively. RESULTS SS is characterized by high expression of IL-17E and iNOS in the epidermis, while PG exhibits low expression. The neutrophil infiltrate helps to differentiate PP (high density) from PSO (low density). High expression of Arginase1 in the granular layer of the epidermis is a hallmark of SPD. Finally, mature neutrophils and pro-inflammatory macrophages are readily detectable in PP, SPD, PG while immature neutrophils and anti-inflammatory macrophages are more frequent in GPP, AGEP, HS, and SS. CONCLUSIONS The analysis of ND by immunofluorescence using IL-17E, iNOS and Arginase1 in combination with MPO and CD68 allows the characterization of differential expression patterns in the epidermis as well as the determination of the polarization status of the dermal neutrophils and macrophages. The respective markers may help in the differentiation of ND in clinical routine.