Crossover features of heterochronic parabiosis pairs. (A) Crossover scheme to track the percentage of B6 cells in BJ parabionts or BJ cells in B6 parabionts. (B) Blood (left), BM (middle), and HSC (right) crossover in indicated mice. (C) Complete blood count (CBC) analyses in indicated mice. WBC, white blood cells; Neut., neutrophils; Lymph., lymphocytes. (D) Lineage distribution analyses in the blood of indicated mice. (E) Crossover scheme to track the percentage of B6 GFP⁺ cells in young and old B6 parabionts. (F) Blood (left), BM (middle), and HSC (right) crossover in the indicated mice. Data are means ± SD; *, P ≤ 0.05.