Nephritic Factor: Its Structure and Function and Its Relationship to Initiating Factor of the Alternative Pathway

Abstract

Nephritic factor (NF) [human] has a MW of 170,000 and is composed of 2 disulfide-linked 85,000-dalton chains. NF assembles the fluid-phase C3 [the 3rd complement component] convertase from Factors B and D, C3 and Mg by physically incorporating itself into the enzyme complex. NF exerts its stabilizing effect on the cell-bound C3/C5 convertase, .**GRAPHIC**. [activated c3b, factor B complex bound to erythrocytes], by physically associating itself with this complex. On decay of the cell-bound enzyme, NF is released into the fluid phase and retains its binding and stabilizing potential. Its activity is resistant to diisopropylfluorophosphate treatment. Because NF causes agglutination of .**GRAPHIC**. it must be endowed with more than 1 binding site.