Interleukin-4 induces homotypic aggregation of human mast cells by promoting LFA-1/ICAM-1 adhesion molecules

We report here that interleukin-4 (IL-4) Induces homotypic aggregation of cultured human mast cells, grown from cord blood mononuclear cells in the presence of stem cell factor and IL-6. This aggregation was specifically induced by IL-4, because other cytokines including IL-1 alpha, IL-1 beta, IL-2, IL-3, IL-5, IL-9, IL-10, interferon-gamma, IL-12, granulocyte-macrophage colony-stimulating factor, NGF-beta, and tumor necrosis factor alpha failed to show such effect. Flow cytometric analysis of the cultured mast cells showed that IL-4 increases the expression of lymphocyte function-associated antigen-1 (LFA-1) and intercellular adhesion molecule-1 (ICAM-1), but not of very late antigen (VLA) family adhesion molecules or vascular cell adhesion molecule-1 (VCAM-1). Neutralizing monoclonal antibodies specific for LFA-1 alpha, LFA-1 beta, of ICAM-1 inhibited the IL-4-induced homotypic aggregation of the mast cells, indicating that the aggregation was mediated mainly by LFA-1/ICAM-1 interaction. In addition, IL-4-treated but not untreated mast cells bound to immobilized ICAM-1. This binding was also inhibited by anti-LFA-1 or anti-ICAM-1. Theses results show that IL-4 promotes expression of ICAM-1 and LFA-1 molecules on mast cells, and suggest that IL-4 may contribute to the migration of mast cells into the inflamed tissue and to the cellular interaction with other inflammatory cells by upregulating adhesion molecules. (C) 1997 by The American Society of Hematology.