Different profile of interleukin-10 production in circulating T cells from atopic asthmatics compared with healthy subjects

Background: Interleukin (IL)-10 is a pleiotropic cytokine released from various cells, including T cells. Although IL-10 is suggested to inhibit allergic responses, its role in asthma remains uncertain. The purpose of the present study was to compare the profile of IL-10 in circulating T cells from stable atopic asthmatics, atopic nonasthmatics and healthy controls. Methods: Peripheral blood mononuclear cells were isolated, stained with anti-CD3 and CD4/CD8 antibodies, and then processed for intracellular IL-10 detection by flow cytometry. Results: A kinetic study in healthy controls showed that stimulation with phorbol 12-myristate 13-acetate and ionomycin significantly increased the frequencies of IL-10-producing CD³⁺, CD4 ⁺ and CD8⁺ cells. Without stimulation, the frequencies of IL-10-producing CD3⁺, CD4⁺ and CD8 ⁺ cells were significantly higher in asthmatics than in healthy controls, while a similar trend was observed in atopic nonasthmatics. Stimulation for 24 h significantly increased IL-10-producing CD3⁺, CD4⁺ and CD8⁺ cells in healthy controls and atopic nonasthmatics, but not in asthmatics. Conclusions: The frequency of IL-10-producing T cells is increased in the circulation of stable atopic asthmatics compared with normal controls. The lack of enhancement in their frequency by phorbol 12-myristate 13-acetate and ionomycin in asthmatics suggests that the circulating T cells of asthmatic subjects are maximally stimulated with regards to IL-10 production; alternatively, IL-10 production by T cells from asthmatics may be regulated differently than T cells from other subjects.