Western analysis of protein extracts from LCLs established from patients listed in Table. 1. A & B. Basal levels of the ATM protein. C. ATM protein levels before and 1 hour after an IR exposure of 5 Gy. Western blots were probed with the ATM-2C1 antibody (Abcam). Obligate A-T heterozygote (ATH); Highest ATM expresser (HE); Non-reactor controls (C1-3).