To explore the potential role of circulating TFH cells in EV71-mediated HFMD children, the frequency of circulating CXCR5+CD4+ TFH cells and the percentages of ICOShigh or PD-1highCXCR5+CD4+ TFH cells were analyzed using flow cytometry (Figures 1(a)–1(c)). This evidence concerns the gene CD4 and hand, foot and mouth disease.