Expression of mu and gamma immunoglobulin heavy chains in different cells of a cloned mouse lymphoid line.

A cloned cell line derived from mouse bone marrow and transformed by Abelson virus is shown to synthesize two different heavy chains, mu and gamma 2B, in vitro. This characteristic is stable because it persists upon subcloning. Although most of the immunoglobulin-synthesizing cells produce either mu or gamma 2B heavy chains, a few cells contain both heavy chains, suggesting immunoglobulin class switching. Karyotypes show a complement of 41 chromosomes. Two copies of chromosome 12, to which immunoglobulin heavy chain structural genes have been assigned, were found. No light chain was found in either the mu- or the gamma 2B-producing cells. However, fusion of the cell line with a myeloma that synthesizes neither heavy nor light chains caused expression of kappa light chain in the hybridoma synthesizing mu chain. No light chain could be detected in the hybridomas synthesizing gamma 2B heavy chain.