IL-13 over-expression in skin is not confined to IgE-mediated skin inflammation.

Abstract

IL-13 is produced by T cells and, like IL-4, it can induce the production of IgE and IgG4. In order to investigate if IL-13 is a specific marker for atopic dermatitis (AD), IL-13 gene expression was analysed in chronic lichenified lesions and non-lesional skin of patients with AD, in involved and non-involved skin of patients with psoriasis, in positive tuberculin reactions in non-atopics, and in the skin of healthy control subjects. Patients with AD (n = 9) showed sensitization to common air-borne allergens (positive Phadiatop) and had total serum IgE values in the range from 10 to 4800 kU/l (median 170 kU/l). Competitive reverse transcription-polymerase chain reaction (RT-PCR) was used to assess IL-13 gene expression in skin biopsy specimens. IL-13 gene expression was markedly higher in chronic lichenified lesions of patients with AD (P < 0.01), and in the positive tuberculin reactions (P < 0.01; n = 12) than in skin from healthy control subjects (n = 10). However, there was no significant difference in IL-13 gene expression in the skin of patients with psoriasis (n = 10) and that of healthy control subjects. The dermal cell infiltrates were larger and the relative amount of CD3+ and CD4+ cells in these infiltrates was higher in the skin of subjects with a positive tuberculin reaction than in lichenified AD skin. However, these differences were not reflected in differences in IL-13 gene expression. Different triggers of IL-13 gene expression may influence the diverse patterns of inflammation seen in different inflammatory skin disorders.