Structure and diversity of Mexican axolotl lambda light chains

We report here the structure of cDNA clones encoding axolotl light chains o f the lambda type. A single IGLC gene and eight different potential IGLV ge nes belonging to four different families were detected. The axolotl C lambd a domain has several residues or stretches of residues that are typically c onserved in mammalian, avian, and Xenopus C lambda, but the KATLVCL stretch , which is well conserved in the C lambda and T-cell receptor C beta domain s of many vertebrate species, is not well conserved. All axolotl V lambda s equences closely match several human and Xenopus V lambda -like sequences a nd, although the axolotl C lambda and V lambda sequences are very like thei r tetrapod homologues, they are not closely related to nontetrapod L chains . Southern blot experiments suggested the presence of a single IGLC gene an d of a limited number of IGLV genes, and analysis of IGLV-J junctions clear ly indicated that at least three of the IGLJ segments can associate with IG LV1, IGLV2, or IGLV3 subgroup genes. The overall diversity of the axolotl V lambda CDR3 junctions seems to be of the same order as that of mammalian V lambda chains. However, a single IGLV4 segment was found among the 45 cDNA s analyzed. This suggests that the axolotl ICL locus may have a canonical t andem structure, like the mammalian IGK or IGH loci. Immunofluorescence, im munoblotting, and microsequencing experiments strongly suggested that most, if not all L chains are of the lambda type. This may explain in part the p oor humoral response of the axolotl.