['Intravenous immunoglobulin (IVIG) therapy has been reported to be effective for reducing the incidence of coronary artery lesions in Kawasaki disease (KD), an acute febrile vasculitis of unknown aetiology. Regarding the mechanism of IVIG in immune thrombocytopenic purpura (ITP), it has been reported that IVIG increases the expression of the inhibitory Fc receptor, FcgammaRIIB (CD32B), on splenic macrophages in a murine ITP model. Regarding the mechanism of IVIG during acute KD, we investigated whether or not IVIG increases the expression of FcgammaRIIB in peripheral blood CD14+ monocytes/macrophages.', 'The expression of FcgammaRIIB in peripheral blood CD14+ monocytes/macrophages was determined before and after IVIG therapy in 13 patients with acute KD by flow cytometry.', 'The percentage of CD14+ CD32B+ monocytes/macrophages among peripheral blood mononuclear cells, the absolute number of CD14+ CD32B+ monocytes/macrophages and the percentage of CD14+ CD32B+ monocytes/macrophages among CD14+ monocytes/macrophages in patients with acute KD before IVIG therapy were significantly increased compared with those after IVIG therapy and in controls. CD14+ CD32B+ monocytes/macrophages decreased to within the normal range soon after IVIG therapy.'] Does intravenous immunoglobulin increase FcgammaRIIB expression on monocytes/macrophages during acute Kawasaki disease?