Quantitation of constant and variable region genes for mouse immunoglobulin λ. chains

Abstract

CDNA [complementary DNA] was synthesized complementary to purified mRNA derived from the .lambda. chain producing myeloma tumor, RPC-20. This cDNA is of sufficient length to encode the constant region and a major portion of the variable region sequence of the .lambda. gene. The expected range of cross-hybridization of this .lambda. probe extends to several different members of the closely related .lambda. subgroup, as well as to a member of the .lambda. subgroup represented by MOPC-315. Since there are a minimum of 7 known members of the common .lambda. subgroup in addition to MOPC-315 [myeloma], these sequences, in accordance with the germ line hypothesis, must be represented by a minimum of 8 variable region genes. Using the RPC-20 cDNA probe and hybridization kinetic analysis, this sequence was represented as approximately 2 copies per haploid genome in DNA derived from a variety of .kappa.- and .lambda.-producing tumors and normal tissue. Inasmuch as the cross-hybridization range of the probe was assessed and a minimum size of the .lambda. subgroup determined, this observation tends to rule out separate germ line genes corresponding to each individual .lambda. L chain variant.