Figure 3: Increased numbers of 53BP1 foci in non-irradiated brain tissue from repair-deficient (ATM-/- and SCID) mice. Immunofluorescent staining for 53BP1 (green) demonstrated increased foci relative to repair-proficient (ATM+/+) mice. Original magnification, 600×. Quantification of 53BP1 foci in nonirradiated tissues of C57BL/6, ATM+/+, ATM-/- and SCID mice. Data are presented as means from three different experiments ± standard error. (* denotes a statistically significant difference compared to C57BL/6 mice, ** to ATM+/+ mice).