ICOS and Schistosomiasis japonica: Next, we compared the frequencies of total peripheral memory Tfh cells (CXCR5+CD45RA-CD4+ T cells) [16] and activated peripheral memory Tfh cells (PD-1+ICOS+Tfh cells) [17,18] among CD4+ T or total peripheral memory Tfh cells in 50 patients with schistosomiasis japonica to 50 healthy controls.