Heavy-chain gene rearrangements in EBV-transformed cell lines analyzed by Southern blot. DNA from EBV lines was digested with EcoRI and HindIII and probed with a J6 fragment. The DNA in lane 1 is from a T-cell line; the line from patient 1 is shown in lane 2. Lanes 3-6 contain DNA from lines from patient 2. The DNA in lane 7 is from the EBV line from patient 3. The DNA from the 4 polyclonal lines from patient 4 is shown in lanes 8-11. The DNA in lanes 12-14 is from lines from patients with XLA. The DNA in lanes 15-18 is from lines from healthy controls.