EXPRESSION OF IMMUNOGLOBULIN CHI AND LAMBDA CHAINS IN MINK

The ratio of kappa and lambda chains of immunoglobulins varies signifi cantly from one species to another. It has previously been thought tha t lambda was only type expressed in mink. We tested mink immunoglobuli n light chains using two monoclonal antibodies G80 and G88. It has bee n shown that G80 and G88 specifically recognize two antigenically diff erent subpopulations of the light chains. Immunochemical analysis of t hese subpopulations separated by affinity chromatography suggested tha t they represent lambda and kappa types of light chains, respectively. Screening of a mink cDNA library with monoclonal antibody G88 resulte d in the isolation of clone pIGK-1 containing kappa chain-encoding seq uence. The cDNA insert of pIGK-1 included most of the V segment, as we ll as the J, C and 3' untranslated sequences. Mink Vkappa sequence sho wn the highest homology with the human VkappaII subgroup genes (76-79 %). Mink Ckappa sequence was 53-63 % homologous to Ckappa of other spe cies. The striking feature of mink Ckappa chain is the presence of glu tamine in the C-terminal position. Southern blot analysis suggested th at mink haploid genome has one Ckappa gene and multiple Vkappa genes. The kappa : lambda chain ratio in the 12 minks studied was, on the ave rage, 46 : 54. The same ratio was observed for the kappa- and lambda-p roducing cells in the mesenteric lymph nodes. The five previously iden tified mink light chain allotypes were assigned to the lambda chains, thereby confirming that lambda chains in this species are additionally subdivided into several subtypes.