In this study, the frequency of circulating CXCR5+CD4+TFH cells with inducible costimulator (ICOS) expression in the children with acute HSP was significantly higher than that in healthy controls (HCs) but not CXCR5+CD4+TFH cells with programmed death-1 (PD-1) expression. The gene discussed is PDCD1; the disease is hereditary spastic paraplegia.