Immunoglobulin heavy-chain class switching in a pre-B cell line is accompanied by DNA rearrangement.

Switching of an Abelson virus-transformed mouse lymphoid cell line from immunoglobulin mu to gamma 2b heavy-chain synthesis in vitro is accompanied by loss of DNA sequences between the JH and C gamma 2b gene segments, and thus cannot be explained by differential RNA processing. The light-chain loci of both mu- and gamma 2b-producing cell clones are in the embryonic configuration, which indicates that class switching can occur in pre-B cells.