NEONATAL-V(H), NEONATAL-D, AND NEONATAL-J(H) GENE USAGE IN RABBIT B-LINEAGE CELLS

The neonatal antibody repertoire in both mouse and humans differs from that of the adult repertoire in that the neonatal repertoire uses a l imited set of J(H)-proximal V(H) genes but the adult repertoires use m any different V(H) genes. Rabbits are unusual in that adults use only three or four V(H) genes, with approximately 80% of the B cells using V(H)1, the 3'-most V(H) gene. To investigate whether the repertoire of neonatal rabbits differs from that of adults, we analyzed V(H), D, an d J(H) gene usage in B cells of neonatal rabbits. A total of 68 rearra nged VDJ genes was cloned from mRNA and genomic DNA isolated from lymp hoid tissues of newborn to 10-day-old rabbits. We found that 74% of th e VDJ gene rearrangements utilized V(H)1 and 15% utilized the genes th at we designated V(H)x or V(H)y. From the remaining VDJ genes we ident ified seven novel V(H) genes, one, V(H)z, which was found in mRNA. We conclude that the repertoire of utilized V(H) genes in neonates is lim ited and is similar to that of adult rabbits. We also found the D1, D2 a, D2b, and J(H)4 gene segments preferentially rearranged. We suggest that the preferential usage of V(H), D, and J(H) gene segments in VDJ genes is caused by preferential rearrangement rather than by selective expansion of B cells that utilize the gene segments.