Restriction map of germline IGHJ region showing restriction sites used in digests together with site and orientation of oligonucleotide primers. Sequence information used to design the oligonucleotide primers was derived from published sequences.26 29-32 The position of the 5′ end of the oligonucleotide primers is indicated with respect to the 5′ BamHI site. Xho I and Sal I sites within J6I are underlined. B, BamHI; Bg, Bgl II; H, HindIII; P, Pst I; S, Sac I; X, Xba I.