Adaptation of the Zymosan Assay of Properdin to Animal Sera

Abstract

The reaction of zymosan with properdin of certain animal species was found to be inhibited in the presence of properdin-free human complement (RP), an essential reagent in the standard assay. The problem was resolved by (1) precipitating the properdin as euglobulin and reconstituting for the assay in properdin-free residues (R3 or endpiece) of human complement, or (2) deferring the addition of RP until properdin-zymosan complex had formed. The methods were applied successfully in the assay of guinea pig, swine, and canine properdin, but were ineffective in demonstrating properdin in chicken serum.