Murine complement factor B (BF): sexual dimorphism and H-2-linked polymorphism.

Polymorphism of murine BF is described using agarose gel electrophoresis of EDTA-plasma. The proteins were blotted onto cellulose nitrate sheets and BF was detected by incubation of these sheets with anti-BF serum, anti-IgG serum, and 125I-labeled protein A successively. After autoradiography, four or five main BF bands were found in plasma of male mice. The strain WLL/BrA (H-2bs) carried a more anodal variant than the strains 020/A(H-2pz), B10 (H-2b), B10.A (H-2a), B10.M (H-2f), and OIR (H-2q). In backcross and F2 generations the BF variants always cosegregated with the H-2 haplotypes. In this way linkage to H-2 could be established. When the electrophoretic BF patterns of males and females were compared, a sexual dimorphism was discovered; the females of each strain had only three main BF bands compared with the four or five found in males. However, no difference in level between males and females could be detected, probably because the three BF bands in the females were stronger. These data extend the information on the interspecies homology of the MHC and may open new possibilities for studies of the genetic organization and hormonal regulation of the H-2 complex.