Immune regulation by CD4+CD25+ T cells and interleukin-10 in birch pollen-allergic patients and non-allergic controls

CD4(+)CD25(+) regulatory T (Treg) cells and the cytokines IL-10 or TGF-beta play key roles in the maintenance of T cell homeostasis and tolerance to infectious and non-infectious antigens such as allergens. To investigate the regulation of immune responses to birch pollen allergen compared with influenza antigen by Treg cells obtained from birch pollen-allergic patients and non-allergic controls. Peripheral blood was collected from 10 birch pollen-allergic patients and 10 non-allergic healthy controls. CD4(+)CD25(+) and CD4(+)CD25(-) cells isolated by magnetic-activated cell sorting were co-cultured and stimulated with birch pollen extract or influenza vaccine in the absence or presence of anti-IL-10 or soluble TGF-beta RII. CD4(+)CD25(+) cells from non-allergic controls were able to suppress influenza antigen and birch pollen stimulated effector cell proliferation, whereas CD4(+)CD25(+) cells from allergic patients suppressed influenza antigen-, but not birch pollen-stimulated proliferation. The production of Th1 cytokines, but not Th2 cytokines, was suppressed by CD4(+)CD25(+) cells from both allergic patients and controls, upon stimulation with birch pollen extract. Neutralization of IL-10 led to significantly increased production of IFN-gamma in cultures with CD4(+)CD25(-) T effector cells. In addition, six-fold higher concentrations of TNF-alpha were detected after neutralization of IL-10 in both CD4(+)CD25(-) and CD4(+)CD25(+) cell cultures from allergic patients and controls. We demonstrate that the allergen-specific suppressive function of CD4(+)CD25(+) cells from allergic patients is impaired compared with non-allergic controls. Moreover, neutralization of IL-10 enhances the production of TNF-alpha, suggesting counter-acting properties of IL-10 and TNF-alpha, where IL-10 promotes tolerance and suppression by Treg cells and TNF-alpha promotes inflammatory responses.