Intravenous immunoglobulin therapy induces neutrophil apoptosis in Kawasaki disease

To investigate the effect of high-dose intravenous immunoglobulin (IVIg) on neutrophil apoptosis in Kawasaki disease (KD), we studied the in vitro spontaneous and IVIg-induced apoptosis of neutrophils by analyzing a proportion of annexin V-positive cells and cells with fragmented DNA. The mean number of peripheral neutrophils in the post-IVIg phase decreased significantly (P < 0.01) compared with that in the pre-IVIg phase. The mean proportion of spontaneous apoptotic neutrophils in the post-IVIg phase was significantly higher (P < 0.01) than that in the pre-IVIg phase, and there was a significantly positive correlation (P < 0.01) with the reduction ratio of the circulating neutrophil counts from the pre-IVIg through the post-IVIg phases. IVIg induced a dose-dependent increase in the proportion of apoptotic neutrophils in the pre-IVIg phase. As a result, the present study demonstrated a novel action in which high-dose IVIg therapy decreased the number of circulating neutrophils by accelerating their apoptosis in KD.