Frequency of CAFC subsets in old mice compared with their young counterparts. Mean frequencies of CAFC day 7, 14, 21, 28, and 35 in old C3H/He (•, 1 experiment, 5 mice), CBA/J (*, 3 experiments, 15 mice), DBA/2 (▴, 1 experiment, 5 mice), BALB/c (▪, 3 experiments, 15 mice), and C57BL/6 (♦, 2 experiments, 9 mice) mice. Data are expressed as percentage of CAFC values found in young mice. (A) The CAFC frequencies per 10⁵ marrow cells; (B) values per femur. Control frequencies in young mice for each cell type per 10⁵ marrow cells were: C3H/He: day 7: 124, day 14: 61, day 21: 7.54, day 28: 2.14, day 35: 0.65. CBA/J: day 7: 110, day 14: 31.4, day 21: 5.34, day 28: 1.40, day 35: 0.50. DBA/2: day 7: 125, day 14: 77, day 21: 13.4, day 28: 7.61, day 35: 1.55. BALB/c: day 7: 80, day 14: 50.4, day 21: 11.8, day 28: 2.74, day 35: 0.87. C57BL/6: day 7: 123, day 14: 18.5, day 21: 4.96, day 28: 2.61, day 35: 1.01. Control values for (B) can be calculated using these data and the data given in Table 1.