Studies on the Properdin System: Isolation of a Heat-Labile Factor from Guinea Pig Serum Related to a Human Glycine-Rich Beta-Glycoprotein (Gbg or Factor B)

Abstract
A heat-labile factor (HLF), which is essential for C3 inactivation by purified cobra venom factor, has been isolated from guinea pig serum. In addition to HLF, other protein(s) are required for inactivation of C3 by the cobra venom factor. HLF has a molecular weight of about 100,000 and is antigenically related to the human glycine-rich beta-glycoprotein (GBG). HLF is believed to be the guinea pig counterpart of factor B of the human properdin system.