However, the correlation between the elevated level of ICOS+cTfh or IL-21+ICOS+cTfh cells with memory B cell subsets during acute HIV-1 infection stage in our results (Figures 3, 4) indicated that signaling via ICOS after cTfh activation may drive the memory B cell perturbation as early as primary infection stage. This evidence concerns the gene ICOS and HIV-1 infection.