CFB Gene

The CFB gene (CFB stands for "Complement Factor B") is a protein coding gene located at chromosome 6p21.33. The CFB gene encodes complement factor B, a component of the alternative pathway of complement activation. The CFB gene is localized in the major histocompatibility complex (MHC) class III region on chromosome 6. This cluster includes several genes involved in the regulation of the immune response.

Factor B circulates in the blood as a single-chain polypeptide. Upon activation of the alternative pathway, it is cleaved by complement factor D, forming the non-catalytic chain Ba and the catalytic subunit Bb. The active subunit Bb is a serine protease that combines with C3b to form the C3 convertase of the alternative pathway. Bb is involved in the proliferation of preactivated B lymphocytes, whereas Ba inhibits their proliferation.

Diseases associated with CFB include:

• atypical hemolytic uremic syndrome (OMIM: 612924)

and

• complement factor B deficiency (615561). Complement factor B deficiency is associated with increased susceptibility to infections (meningococcal, pneumococcal).

1. Carreras L et al (1981) Familial hypocomplementemic hemolytic uremic syndrome with HLA-A3, B7 haplotype. JAMA 245: 602-604.
2. Esparza-Gordillo J et al. (2005) Predisposition to atypical hemolytic uremic syndrome involves the concurrence of different susceptibility alleles in the regulators of complement activation gene cluster in 1q32. Hum Molec Genet 14: 703-712.
3. Goicoechea de Jorge EG et al (2007) Gain-of-function mutations in complement factor B are associated with atypical hemolytic uremic syndrome. Proc Nat Acad Sci 104: 240-245.
4. Slade C et al (2013) Deficiency in complement factor B. (Letter) New Eng J Med 369: 1667-1669.