Asthma is characterised by the expression of multiple inflammatory genes. Interleukin-10 (IL10), an anti-inflammatory cytokine, inhibits the synthesis of proinflammatory cytokines, chemokines, and inflammatory enzymes in activated macrophages, T cells, and human polymorphonuclear leucocytes. 1 Production of IL10 is decreased in alveolar macrophages and peripheral blood mononuclear cells of patients with asthma, 2 which could explain the proinflammatory profile in these patients and may lead to the development of more severe disease.