Interleukin (IL)-10 has anti-inflammatory activities in various immune reactions and plays an important role in the regulation of immune diseases. In the present study, we examined the role of IL-10 in atopic diseases. Peripheral blood mononuclear cells (PBMCs) from healthy control subjects, patients with atopic dermatitis and patients with bronchial asthma were cultured with lipopolysaccharide (LPS). The production of IL-10, IL-12 or IFN-γ by PBMCs stimulated with LPS was measured. Next, we investigated whether the haplotype in the IL-10 gene promoter region had an effect on the production of IL-10 by PBMCs. PBMCs from patients were cultured with phytohemagglutinin, to which recombinant human IL-10 had been added. IL-12, IFN-γ and IL-4 production by PBMCs was measured. β-lactoglobulin (BLG)-specific T cell clones were cultured with BLG peptide (P-17), antigen-presenting cells and recombinant human IL-10. The antigen-induced proliferation of the T cell clones and cytokine production were assayed. Results demonstrated that IL-10 production by LPS-stimulated PBMCs was lower in atopic patients than in healthy control subjects. Three different haplotypes in the IL-10 gene promoter region were detected. These haplotypes did not correlate with IL-10 production by PBMCs. IL-10 inhibited Th1 cytokine production by PBMCs, and also inhibited the antigen-induced proliferation of T cell clones and Th2 cytokine production. In conclusion, IL-10 inhibits both the production of Th1 and Th2 cytokines and the antigen-induced proliferation of T cell clones. Thus, IL-10 modulates other cytokines and plays an important role as an immune-modulator in the pathogenesis of atopic diseases.

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