KGF administration enhances thymopoiesis and peripheral T-cell development in 18-month-old mice. Eighteen-month-old CBA mice received 5 mg/kg KGF or PBS subcutaneously on 3 consecutive days. Mice were harvested 14 days after KGF administration, and thymic and splenic cellularity were determined. (A) Thymic and splenic cellularity are depicted. (B-C) Thymic subpopulations were calculated as described in Figure 1. (D) Splenic T-cell numbers were determined as described in Table 1. (E) Splenocytes were stained with anti-CD4, -CD8, and -CD44 antibodies, and the percentages of T cells (naive CD4, CD4⁺CD44^-; memory CD4, CD4⁺CD44⁺; naive CD8, CD8⁺CD44^-; and memory CD8, CD8⁺CD44⁺) were determined by multicolor flow cytometry. Values represent mean (± SEM) and n = 4-8 per group. ^*P < .05.