KGF treatment increases the number of T cells and T-cell–dependent antibody production in the periphery. (A) Blood was drawn from young or aged mice (n = 5-7 per group) 1 month after PBS or KGF treatment, and analyzed for mature CD4⁺ and CD8⁺ T cells. ⊡ indicates PBS-treated aged mice; □, KGF-treated aged mice. *P < .05, PBS versus KGF. (B) The mean absolute cell number ± SD of naive CD4⁺ T cells that were CD45RB^high and CD44^low in the blood from PBS- or KGF-treated young or aged mice (n = 5-7 per group). *P < .05, PBS versus KGF. (C) KLH-specific IgM and IgG1 titer in young and aged mice. Mice were immunized with KLH at day 31 and day 45 after initiation of PBS or KGF treatment. Anti-KLH titer (mean ± SD shown) was measured 2 weeks after each immunization (n = 7 per group). *P < .05, PBS-treated aged mice versus KGF-treated aged mice; NS indicates not significant.