Diversification of sheep immunoglobulins

The sheep antibody repertoire was assessed by sequence analysis of Vλ, Vκ and VH cDNA clones. In fetuses, all immunoglobulin chains were essentially in germline configuration, although limited diversity occurred at the junctional regions of Vκ chains. Fetal B cells expressed 12 distinct Vλ and six Vκ gene segments. VH gene segments were also in germline configuration in fetuses but became extensively mutated with advancing post natal age. Two distinct types of mutations, point mutations and block mutations, were detected in VH transcripts and these localised differently along the gene. This raises a question as to whether a novel mutational mechanism may be involved in VH diversification in sheep.