Infiltrating cells, related cytokines and chemokine receptors in lesional skin of patients with dermatomyositis

Summary Background There have been only two reports on immunophenotypic characterization in the cutaneous lesions of dermatomyositis (DM) that emphasize the importance of the infiltrating CD4+ T lymphocytes. Objectives To characterize the immunophenotype of the cells that infiltrate the lesional skin of DM and to evaluate the possible T‐helper (Th) polarization Th1/Th2 through detection of specific cytokines, chemokine receptors and markers of cellular activation. Methods Skin biopsy specimens derived from pathognomonic lesions (Gottron's papules and Gottron's sign) of eight patients with DM were immunostained with a large panel of monoclonal antibodies to CD3, CD4, CD8, myeloperoxidase (MPO), eosinophil cationic protein, tryptase, CD40, CD40 ligand (CD40L), HLA‐DR, interleukin (IL)‐2, IL‐4, IL‐5, IL‐13, interferon‐γ, tumour necrosis factor‐α, receptor 3 for CXC chemokines (CXCR3) and receptor 3 for CC chemokines, using the alkaline phosphatase–antialkaline phosphatase method. Control specimens were obtained from five healthy subjects and from six patients with discoid lupus erythematosus. Results Activated CD4+ Th lymphocytes (HLA‐DR+ CD40L+) were the principal infiltrating cells in the lesional skin of DM; the CD4/CD8 ratio was approximately 2·5. A mixed Th1/Th2 profile and higher Th1 cytokine production together with significant staining for CXCR3 were detected. Neutrophil granulocytes were the second most abundant population; eosinophil granulocytes were very poorly represented. Conclusions Activated CD4+ T cells presumably mediate the main pathogenetic mechanisms in pathognomonic skin lesions. The interaction between CD40 and CD40L could be an important mechanism of cellular activation in cutaneous immune‐mediated inflammation by induction of secretion of proinflammatory cytokines and chemokines. Neither Th1 nor Th2 clear polarization was found, although there was a slight Th1 prevalence. There was a significant quantity of MPO+ cells (neutrophil granulocytes) in the inflamed tissue, and they might have a role in sustaining the chronic inflammation.