The immunoglobulin lambda light chain locus in inbred mice contains a limited number of germline genes. However, recent studies of lambda genes in populations of wild mice have revealed that these mice may have an amplified number of lambda genes, as judged by cross-hybridization of DNA restriction fragments with lambda probes derived from inbred strains. It is not known, however, whether these putative lambda genes are functional. To obtain further insight into the evolution of the lambda locus, the organization and expression of these genes in wild-derived mice is being examined. The approach is to prepare lambda- producing hybridomas which are a source of rearranged lambda genes and their expressed products. Several hybridomas have been identified that appear to produce lambda chains that differ substantially from those in BALB/c. The variable region of one of these chains, from a mouse from Skive Denmark (SD), differs so greatly in sequence from any known V-lambda that cross- hybridization of the corresponding genes would not be expected. Such a gene would have escaped detection in earlier studies. To pursue these findings, a cDNA library has been prepared from the SD hybridoma. The sequence of clones encoding the unusual lambda chain has been determined. The V region of the SD lambda chain is only about 40% identical in amino acid sequence to the lambda 1 V region. Next, unrearranged lambda genes will be characterized in a DNA library that will be prepared from SD kidney. The results should indicate the extent of somatic mutation in the gene encoding the SD26 V segment. Hybridization probes corresponding to V lambda SD26 will be used to evaluate the possible presence and expression of related genes in other wild mice and in laboratory strains of inbred mice. The expression of other, previously unrecognized lambda genes will be sought by examining additional lambda-producing wild mouse hybridomas. Although inbred mouse strains are regularly used in studies of the regulation and function of the immune response, relatively few studies have compared the organization and function of the immune system in inbred mouse strains and wild mice. The mechanisms by which a great diversity of antibodies is generated to recognize a wide array of possible foreign molecules is fundamental to our understanding of immune function. Previous results from this laboratory have revealed interesting and provocative differences between the genes encoding antibody light chains in wild mice and those in inbred strains. Further results of this research should shed new light on the organization and evolution of immunoglobulin genes.
