Structural polymorphism of murine factor B controlled by a locus closely linked to the H-2 complex and demonstration of multiple alleles.

New alleles of murine factor B (Bf) protein were demonstrated. When ethylenediaminetetraacetic acid (EDTA)-plasmas from inbred and wild mice were analyzed by isoelectrofocusing (IEF) and immunofixation, murine Bf proteins were visualized as distinct protein bands in all mice tested. Four variants of murine Bf could be demonstrated in a large number of tested mice: Bf 1 (isoelectrofocusing point (P.I.) range of 5.8-6.1) exemplified by B10 and B10.BR, Bf 2 (P.I. range of 5.8-6.0) exemplified by B10.MOL (OHM), Bf 3 (P.I. range of 5.6-5.9) exemplified by B10.MOL (TEN2) and Mus musculus (Mus m.) subspecies Chc, Bf 4 (P.I. range of 6.0-6.3) exemplified by Mus m. subspecies Shh. The genetic linkage between S locus and Bf locus was studied with two backcross progenies--[B10.BR X (B10.BR X Mus m. subspecies Chc)F1] and [B10.BR X (B10.BR X Mus m. subspecies Shh)F1]. Totally, 256 backcross progenies were typed for Bf type and for Ss type (plasma level of the fourth complement protein regulated by S locus). The results indicated that murine Bf was controlled by a single codominant locus located close to the H-2 complex because no mouse showing recombination between Bf locus and S locus was found.