Telomeric damage induced foci in B cells from healthy donors and CLL patients. Confocal immunofluorescence analyses of 53BP1 foci and TRF1/53BP1 colocalization (TIF). (A) CLL B cells isolated from one CLL patient were subjected (IR) or no (Co) to 5 Gy γ-IR and fixed for immunostaining 1 hour latter. Median number of 53BP1 foci and TIF per nucleus is shown. (B-C) B cells from 11 healthy donors (Co) and 18 CLL patients (CLL) were immunostained for 53BP1 and TRF1; 53BP foci and TIF were scored after confocal analysis. (B) Box plot showing number of 53BP1 foci (left) and TIF (right) per nucleus; Wilcoxon-calculated P values are indicated in each box plot. (C) Immunofluorescence representing pictures of 53BP1 foci (left), TRF1 labeling (middle), and TIF (right) in B cells from healthy donor (top) and CLL patient (bottom). Arrows indicate TIF; TOTO staining is outlined in the equatorial plane of the nucleus. Detailed of ×60 magnification are shown after z-stack reconstruction (Image J software).