CD45RO, CCR7, and CD28 expression on CD4 + CXCR5 + Tfh cells as well as CD4 + T, CD3 + CD4-T and CD4 + CXCR5-T cells. CD45RO (A), CCR7 (B) and CD28 (C) expression on CD4 + T, CD3 + CD4-T, CD4 + CXCR5 + Tfh as well as CD4 + CXCR5-T cells from young and aged subjects. Blood lymphocytes were first gated, and then CD4 + T (CD3 + CD4+), CD3 + CD4-T, CXCR5 + CD4 + Tfh and CXCR5-CD4+ T cells were analyzed by expression of CD45RO, CCR7 or CD28. Representative results were shown. Thin line: isotype (iso) control, heavy line: young individual (young), filled area: elderly individual (aged).