Total white blood cell count (WBC) and percentages of different blood types in young and old female mice 1 day after 4 Gy X-irradiation. (a) total WBC counts, (b) lymphocytes (%), (c) neutrophils (%), (d) monocytes (%), (e) platelets counts. Data represent the mean S.E.M (n = 3). P values were calculated using the unpaired Student’s t-test. ns: not significant (p ≥ 0.05). YUI, young unirradiated; YIR, young irradiated; OUI, old unirradiated; OIR, old irradiated.