Proteomic Analysis Reveals an Increase of Neutrophils and TH17-related Proteins Expression in Severe Nodular Acne Lesions of the Back

Background: The etiology and different inflammatory steps associated with the development of an acne nodule remain unsolved. Objectives: This study aimed to investigate the main biological processes involved in acne nodules and compare them to those of papules. Methods: Nodules, papules, and non-involved skin of the back (control) were biopsied to perform proteomic analysis using mass spectrometry, Luminex assay, and elastase staining on skin sections. Results: Many factors involved in the migration and function of immune cells, particularly those impacting leukocytes and neutrophils, were strongly and significantly higher in nodules than in papules and non-involved skin, while several enzymes involved in lipid metabolism were lower. Elastase staining confirmed strong neutrophil infiltration within and around the nodules. Conclusions: Our results highlight the role of neutrophils during nodule formation in severe nodular acne of the back.