Properdin factor B polymorphism in Black Americans. 
Properdin factor B is a genetically-controlled polymorphism that can be demonstrated by agarose gel electrophoresis.  The Bf gene frequencies were determined for 194 blacks from the south-eastern United States.  The frequencies for Bf-F, Bf-S, Bf-F1, and Bf-S1 are 0.626, 0.034, and 0.013, respectively.  The south-eastern blacks have similar Bf frequencies to the South African blacks; however, both these groups are different from blacks from Boston.  The frequency differences between south-eastern blacks and Boston blacks may be due to racial admixture differences found in the two populations.