Organization and expression of immunoglobulin genes in fetal liver hybridomas.

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Abstract
The organization and expression of immunoglobulin genes were studied in 6 hybridomas derived from the fusion of a nonproducing myeloma cell with cells from mouse fetal liver. These hybridomas, which exhibit several phenotypic characteristics of immature B lymphocytes, all have productively rearranged .mu. H chain genes and produce the membrane and secreted forms of .mu. mRNA in a ratio of .apprx. 1:10. None of the hybridomas has an unrearranged (germ line) allelic .mu. gene. Examination of the .kappa. L chain genes revealed that all 6 of the hybridomas contain unrearranged .kappa. loci and produce 8.4 kilobase transcripts containing .kappa. constant region sequences. None of the 5 hybridomas that exhibit a .mu.-only phenotype contains a rearranged .kappa. gene other than that derived from the myeloma parent. One hybridoma, which actively secretes .kappa. immunoglobulin, contains a rearranged .kappa. gene of fetal liver origin and synthesizes a distinctive .kappa. mRNA precursor in addition to the 8.4 kilobase transcript. Rearrangement of H chain immunoglobulin genes normally occurs prior to that of L chain genes and further indicate that the transcriptional competence of the .kappa. constant region locus is established prior to the time of its rearrangement.