IL21 and HIV-1 infection: Overall, we found marked expansions of bulk cTfh, ICOS+cTfh and IL-21+ICOS+cTfh cell frequencies, as well as aberrant alterations to memory B cell subsets in peripheral blood occurred during the acute stage of HIV-1 infection, and these abnormalities persisted into chronic infection, consistent with the B cell dysfunction observed in HIV-1 disease.