High content imaging shows distinct macrophage and dendritic cell phenotypes for psoriasis and atopic dermatitis

Psoriasis (Pso) and atopic dermatitis (AD) are chronic inflammatory skin diseases with distinct but also shared immunological features. Assessment of the feasibility of high content immunohistochemistry to identify distinct immune responses in skin biopsies from patients with chronic inflammatory skin diseases. While principal component analysis (PCA) based on the inflammatory marker profile discriminated healthy subjects from patients, it did not differ between Pso and AD. Single-cell phenotyping of high content immunohistochemistry images showed modest disease-specific differences for T cell populations in the number of Th1 T cells and γδT cells. Strong differences in macrophage and dendritic cell (DC) populations were observed whereby in AD disease-specific DCs with antiviral properties and anti-inflammatory macrophages were seen. Additional differences between Pso and AD were seen with the more frequent epidermal localization of CD8⁺ T cells in Pso and DCs in AD. Consequently, high content immunohistochemistry clearly discriminated AD from Pso based on macrophage and DC phenotype. Due to their phenotypic flexibility macrophages and DCs strongly reflect the immunological environment and serve to highlight disease-specific and -defining pathomechanisms and may serve to identify new drug targets.