Novel immunoglobulin heavy chains are produced from DJH gene segment rearrangements in lymphoid cells.

It has been found that most immunoglobulin heavy(H)-chain gene diversity (D) segments carry their own 5' transcriptional promoter element. Transcription of rearrangements which use heavy-chain D and joining (J) segments in B-lymphoid cells ultimately leads to the production of a Dmu messenger RNA which contains the DJH segments linked to the mu heavy-chain constant region. If the D is joined to the JH segment in the appropriate translational reading frame, this Dmu mRNA is translated to yield a short Dmu protein with a variable DJH N-terminus.