Evidence for increased expression of eotaxin and monocyte chemotactic protein-4 in atopic dermatitis

Background: Atopic dermatitis (AD) is a chronic inflammatory skin disease a ssociated with tissue eosinophilia and the activation of T lymphocytes. The novel eosinophil chemoattractants, eotaxin and monocyte chemotactic protei n (MCP)-4, are up-regulated at sites of allergic inflammation, Set their co ntribution to the pathophysiologic mechanisms of AD remains to be determine d. Objective: We sought to investigate the expression of eotaxin and MCP-4 in acute and chronic lesions from patients with AD and to determine their rela tionship to the numbers of resident inflammatory cells. Methods: With use of in situ hybridization, the expression of eotaxin and M CP-4 messenger RNA (mRNA) in skin biopsy specimens from patients with acute and chronic AD skin Lesions was compared with that of uninvolved skin from these patients and skin from healthy volunteers. Results: There was a constitutive expression of eotaxin and MCP-4 mRNA in s kin biopsy specimens from healthy subjects. Positive signal for chemokine m RNA was observed both within the epidermis and inflammatory cells macrophag es, eosinophils. and T cells of the subepidermis in AD skin lesions. Within the subepithelium acute and chronic skin lesions exhibited a significant i ncrease in the numbers of eotaxin and MCP-4 mRNA-positive cells compared wi th uninvolved skin (P < .01), whereas the numbers of eotaxin and MCP-4 mRNA -positive cells were significantly higher in chronic AD compared with acute AD skin lesions (P < .005. P < .001, respectively). Correlations were obse rved between the expression of eotaxin and MCP-4 mRNA and the presence of e osinophils and macrophages, respectively, in AD lesions (r(2) = 0.84, r(2) = 0.94). Conclusion: There is an increased expression of eotaxin and MCP-4 in acute and chronic lesions, suggesting that these chemotactic factors play a major role in the pathophysiologic mechanisms of AD.