We previously reported that the frequency of CD25+CD4+ T cells correlated with FOXP3+CD4+ Treg cells in EGPA patients with severe mononeuritis multiplex or cardiac dysfunction and remained greater than that in EGPA patients without IVIG treatment for as long as 2 years after completion of IVIG therapy [17]. This evidence concerns the gene FOXP3 and eosinophilic granulomatosis with polyangiitis.