V_HD_HJ_H and D_HJ_H gene rearrangements of the 2 Ig-crippled cell lines. (A,C) Shown are the V_HD_HJ_H gene sequences of CB-LCL 4-17 and CB-LCL 5-7-1 from the 5′ end of FR3 to the start of the J_H primer sequence. (B,D) The D_HJ_H gene sequences are depicted from upstream of the recombination signal sequences (RSS; composed of nonamer, 12 base pair [bp] spacer and heptamer) 5′ of the D_H segments to the start of the J_H primer. (A,B) CB-LCL 4-17, (C,D) CB-LCL 5-7-1. N represents N nucleotides. (A) The 2 point mutations giving rise to a nonsense codon in CB-LCL 4-17 are located within the first codon of FR3 and are underlined. (C) CB-LCL 5-7-1 contains a 3-bp and a 51-bp deletion in FR3 that are indicated by black boxes. The 51-bp deletion renders FR3 of CB-LCL 5-7-1 nonfunctional. In this sequence a D_H segment could not be identified but may be part of the sequence marked by N.