Untranslated immunoglobulin kappa light chain mRNA in a lambda light chain-producing mouse myeloma, MOPC104E

Fourteen clones were isolated in culture from a mouse myeloma, MOPC104E. All clones had kappa and lambda types of light chain mRNAs in approximately equimolar quantity as assayed by hybridization with specific complementary DNA (cDNA). However, the myeloma produces and secretes only lambda-type light chain protein. Both kappa- and lambda-type mRNAs in these clones were indistinguishable from kappa- and lambda-type mRNAs of other myelomas with respect to (a) adsorption to oligo-(dT) cellulose, (b) molecular size (12.6 S), and (c) thermal stability of the hybrids formed with corresponding cDNA. The kappa chain mRNA of MOPC104E cells, however, was translated very inefficiently both in vivo and in vitro, whereas the lambda chain mRNA was translated efficiently. These results indicate that each cell of MOPC104E myeloma synthesizes a crippled kappa chain mRNA in addition to a normal lambda chain mRNA.