T helper type 1‐related molecules as well as interleukin‐15 are hyperexpressed in the skin lesions of patients with pyoderma gangrenosum

Summary Pyoderma gangrenosum (PG) is a rare, immune‐mediated skin disease classified into the group of neutrophilic dermatoses. Although a number of studies confirmed the central role of innate immunity, only few studies have investigated the possible contributing role of acquired immunity. In particular, no reports concerning T helper type 1 (Th1) and Th2 cells are available as yet. Therefore, 15 patients with PG, five with Sweet's syndrome (SS) and nine skin specimens from healthy controls (HC) were investigated, evaluating the expression of Th1‐related markers interleukin (IL)‐12, interferon (IFN)‐γ, C‐X‐C motif chemokine receptor 3 (CXCR3) and C‐C motif chemokine receptor 5 (CCR5), of the Th2‐related molecules IL‐4, IL‐5, IL‐13 and CCR3, of the co‐stimulatory axis CD40/CD40 ligand, of IL‐15 and the natural killer (NK) cell marker CD56 in skin lesions by immunohistochemistry. Patients with PG and SS showed a higher expression of Th1 markers than HC. Conversely, IL‐5‐ and CCR3‐expressing cells were less numerous in PG skin lesions compared to SS (P = 0·0157 and