Increased proportion of blood CXCR5 + CD4 + Tfh cells of aged subjects. A. LYM counts: lymphocyte counts of peripheral blood (109/L). B. Percentages of CD4 + T cells (CD3 + CD4+) in lymphocytes from young and aged groups determined by FACS. C. Cell numbers of CD4 + T cells in peripheral blood (109/L). D. Frequencies of Tfh cells (CXCR5 + CD4+) in CD4 + T cells determined by FACS. E. The total cell counts of Tfh cells (CXCR5 + CD4+) in peripheral blood (109/L). F. Correlation of percentages of CXCR5 + CD4 + Tfh cells with age. One open circle or filled square represented one individual. Data were expressed with line at mean with SEM.