Characterization of cultures and dynamics of 53BP-1 nuclear foci formation in dose-escalating IR exposures: In (A), flow cytometry of CAFs after staining cells with α-SMA antibody. Panel (B) shows immunostaining of CAFs with α-FAP. Fluorescence micrographs in (C) show staining with anti-53BP-1 (red/pink) and DAPI (blue). Induction of DNA damage response (DDR) and extent of repair was determined by counting percentage of cells showing nuclear foci staining of 53BP-1 at early (24 h; D) and late (5 days; E) time points. Columns in (D) and (E) each represent average counts from two randomly selected donors (n = 2) (donors #15 and #16). In panel (F), percentage cells with multi-foci (> 9/cell) in (D) and (E) are plotted versus time.