The frequencies of circulating CXCR5+CD4+ TFH cells in CD4+ T cells in both mild (7.00 ± 3.69) and severe (7.15 ± 2.93) HFMD patients were significantly higher than those in HC (4.52 ± 0.65) (Figure 2(a)). This evidence concerns the gene CXCR5 and hand, foot and mouth disease.