Properdin Factor B

The complement system Factor B (FB), also known as C3 Proactivator (C3PA), Properdin Factor B (PFB) or Glycinerich Beta Glycoprotein (GBG), is a glycoprotein that circulates in the blood as a single chain polypeptide with an approximate molecular weight of 93 KDa.
FB is a centrally component of the alternative complement pathway. The activation of this pathway results in factor B cleavage and production of the amino-terminal Ba and the carboxyl-terminal Bb fragments which have a role as cofactors in antibody-independent monocyte-mediated cytotoxicity, macrophage spreading, plasminogen activation and proliferation of B lymphocytes (1).
Factor B hyperconsumption and increased catabolism (that lead to decreased level of this protein in serum), concomitant with factor B fragments production, occurs in several conditions including gram-negative sepsis, kidney diseases (such as chronic glomerulonephritis or lupus nephritis), skin diseases (such as dermatitis herpetiformis or pemphigus vulgaris), autoimmune diseases and sickle cell anaemia (2).
Moreover the genetic Factor B deficiency, a rare condition, determines an increased susceptibility to bacterial infections, particularly Neisseria infections and Streptococcus pneumoniae, due to a defect in the alternative complement pathway activation. (3).


  1. Pekna , Hietala , Landin , Nilsson , Lagerberg, , Betsholtz, and Pekny, (1998), Mice Deficient for the Complement Factor B Develop and Reproduce Normally. Scandinavian Journal of Immunology, 47: 375-380.
  2. Kolb W, P, Morrow P, R, Tamerius J, D: Ba and Bb Fragments of Factor B Activation: Fragment Production, Biological Activities, Neoepitope Expression and Quantitation in Clinical Samples. Complement Inflamm 1989;6:175-204.
  3. Aradottir SS, Kristoffersson AC, Roumenina LT, Bjerre A, Kashioulis P, Palsson R, Karpman D. Factor D Inhibition Blocks Complement Activation Induced by Mutant Factor B Associated With Atypical Hemolytic Uremic Syndrome and Membranoproliferative Glomerulonephritis. Front Immunol. 2021 Jun 10;12:690821.


For Siemens BN™ Analyzer

Product code
KR KR.BNA.GBG-2 Reagent Kit (Calibrator and controls not included)
K K.BNA.GBG-2 Complete Kit
The Properdin Factor B (PFB, GBG, C3PA) “BNA” Kit, when used in conjunction with Siemens “BN™ series” Analyzers (BNA, BN100, BNII, ProSpec), is intended for the quantitative determination of Properdin Factor B in human serum.
Antiserum Reagent
Properdin Factor B R.BNA.GBG-2 1 vial – 4 ml
Complement system proteins W.SPC.CS1 1 vial  – 1 ml
Complement system proteins
Medium Value
Y.SPR.CS1.MV 1 vial  – 1 ml
Complement system proteins
Low Value
Y.SPR.CS1.LV 1 vial  – 1 ml
Complement system proteins
Medium Value
Y.SPR.CS1.MV-3 3 vials – 1 ml
Complement system proteins
Low Value
Y.SPR.CS1.LV-3 3 vials – 1 ml
Reagents included in the kit.
Correlated reagents not included in the kit. They are available separately.