The immunoregulatory and allergy-associated cytokine IL-4, produced by CD4 ' T cells, mast cells and basophils, is actively involved in regulation of different types of inflammation. IL-4 up-regulates humoral inflammatory responses by inducing growth of B cells, isotype switching in activated B cells and differentiation of B cells into antibody producing plasma cells. 16 IL-4 also stimulates the cell-mediated inflammatory processes by promoting growth of activated T cells 17 and enhancing the development of virus-specific cytotoxic T cells. 18 Simultaneously, IL-4 possesses powerful anti-inflammatory effects. In particular, IL-4 controls numerous molecular processes in monocytes, macrophages and neutrophils, which down-regulate production and secretion of the pro-inflammatory cytokines tumour necrosis factor (TNF)-a, IL-1 and IL-8, 19 Á 21 deactivate inflammatory macrophages and lead to suppression of acute inflammation. IL-4 can also induce switching of acute inflammation in the chronic stage owing to its ability to up-regulate expression of the mannose receptor on activated macrophages. 22 The mannose receptor promotes fusion of activated macrophages and formation of giant multinucleated cells in the zone of inflammation 23 that create the cellular background for manifestation of chronic inflammation.