G00008A SINGLE POLYMORPHIC IMMUNOGLOBULIN VH GENE FAMILY IS PREDOMINANTLY EXPRESSED IN THE PERIPHERAL ANTIBODY REPERTOIRE OF CATTLE
Surinder S. Saini*, Wayne R. Hein**, Rob Jacobs* and Azad Kaushik*
Surinder S. Saini*, Wayne R. Hein**, Rob Jacobs* and Azad Kaushik*
*Department of Pathobiology, University of Guelph, Guelph, Ontario, Canada N1G 2W1. **Basel Institute of Immunology, Basel, Switzerland.
Abstract:
In order to understand the generation of antibody diversity in cattle, nine cDNAs, from heterohybridomas secreting bovine IgG1 (2)
and IgM (7) antibodies, were cloned and structurally analyzed for rearranged bovine VDJ genes. All the cloned bovine VH genes shared 83 to
88% nucleotide homology including four other available bovine VH gene sequences. Based upon the criteria of nucleotide homology 80%, all
the bovine VH genes constitute a single VH gene family, which we have designated as bovine VH1 (Bov VH1) gene family. The Bov VH1 gene family
is the most homologous to murine VH Q-52 (72-78%) and human VH4 (67-69%) gene families that belong to mammalian group I/clan II VH genes. In
contrast to murine CDRH3 length distribution of 7 to 12 amino acid residues, the CDRH3 of rearranged bovine VDJ genes were characteristically
long (14 to 56 amino acid). Two bovine JH gene segments, that share most nucleotide homology with human JH4 (82-87%) and JH5 (85%) genes, are
identified and possibility exists for additional bovine JH gene segments. The RNA dot-blot analysis of 44 bovine IgM secreting mouse x cattle
heterohybridomas, originating from mitogen-activated PBLs from bovine leukemia virus infected cattle, revealed that all of these expressed
BovVH1 gene family. An analysis of CDRs provided evidence for somatic hypermutations as an important mechanism for generation of antibody
diversity in cattle. Southern blot analysis of BamH I, EcoR I and Hind III digested genomic DNA from Holstein, Jersey, Hereford and Charolais
breeds of cattle revealed three RFLP patterns and the genomic complexity of Bov VH1 gene family ranged between 13 to 15 genes. These experiments
suggest that the Bov VH1 gene family is predominantly expressed in the peripheral blood lymphocytes of cattle and the somatic hypermutations and
the charasteristic CDRH3 length contribute significantly to the generation of antibody diversity in cattle.
Comments:
Address questions and comments about this abstract to A. Kaushik ( akaushik@ovcnet.uoguelph.ca).
Previously presented at Canadian Socity for Immunology Annual Meeting on March, 1997.