Changes in the peripheral splenic naive and memory T-cell compartments with age. Pie charts show the distributions of naive and memory CD4⁺ and CD8⁺ T cells in WT and Foxn1Tg mice (lines 5 and 60) of 3 different age groups. The percentages of naive and memory cells were calculated based on the average total number of CD3⁺ CD44⁺ T cells per spleen (bottom right in each panel, in millions). Values in parentheses indicate the number of animals in each age group. P values from t test comparing WT and Foxn1 within an age group: *P = 0.038; **P = 0.019; #P = 0.058. NS indicates not significant.