Structure of a third murine immunoglobulin lambda light chain variable region that is expressed in laboratory mice.

Abstract

Recently, we reported evidence for the existence of an immunoglobulin .lambda. light chain (.lambda.x) whose variable region differs from those encoded by the known V.lambda. gene segments V.lambda.1 and V.lambda.2. Expression of of .lambda.x was detected in some hybridomas elicited by treatment of a BALB/c mouse with rabbit anti-.lambda.2 antibodies coupled to bacterial lipopolysaccharide [Sanchez, P. and Cazenave, P.-A. (1987) J. Exp. Med. 166, 265-270]. We constructed a cDNA clone from one hybridoma (B6) that expresses the .lambda.x chain and determined the complete nucleotide sequence. The deduced amino acid sequence of V.lambda.x is 30-33% identical with those encoded by V.lambda.1 and V.lambda.2 and by V.kappa. gene segments. The third hypervariable region of V.lambda.x is four codons longer than those of the other murine variable gene segments. The expression of .lambda.x requires a genomic rearrangement that juxtaposes the V.lambda.x gene with the J.lambda.2-C.lambda.2 joining-constant gene pair. Rabbit anti-V.lambda.x antibodies detected the .lambda.x light chain in the normal sera of all laboratory mice tested. .lambda.x expression seems to be independent of .lambda.1 expression, since both SLJ and SJA strains, which are defective in .lambda.1 production, express normal levels of .lambda.x chain.