Expression of two mRNAs for immunoglobulin lambda chains in the rat

We have analyzed the expression of immunoglobulin lambda chains in the rat by hybridizing RNA from various sources with C lambda 1-like and C lambda 2-like sequences recovered from a rat genomic library. A 1.0 kb lambda 2-like sequence is readily detected in lambda-producing hybridomas and in normal rat spleen RNAs; a 1.0 kb lambda 1-like message is also present, although at much lower levels. An additional 700 b.p. C lambda 2-like fragment is found in all normal rat spleens, and presumably represents a defective message. The nucleotide sequence of one cDNA clone isolated from the lambda-producing hybridoma G36/1 shows a lambda 2-like sequence, and six lambda-secreting hybridomas produced from the spleen of a kappa-suppressed rat all express a C lambda 2-like message. The great majority of rat lambda chains therefore appear to be lambda 2-like. Northern blot analysis of RNA from the spleen of this kappa-suppressed rat shows a considerable increase in the expression of both lambda 2-like and (at lower levels) lambda 1-like message. The coordinate rise of lambda 1 and lambda 2 RNA in this rat suggests that there may be at least two functional lambda chain genes in the rat, although there is as yet no evidence for the existence of rat lambda 1-like proteins.