Cloning and sequencing of the porcine complement factor B.

A genomic clone, SSBf1, containing the complement factor B (BF), a major histocompatibility class III antigen, has been isolated from a porcine genomic library. Partial sequencing and comparison with a human BF gene has identified seven exons coding for amino acids of Ba and Bb, the two subunits of BF. The protein sequence similarity with the human BF is on the average 87%. Southern blot analysis confirmed the existence of only one BF gene per haploid genome. Restriction fragment length polymorphism typing with Taq I showed that there are at least three different porcine BF-haplotypes.