Assay of Properdin in Biological Fluids.

Abstract

A sensitive, reproducible assay for properdin is described based on spectrophotometric determination of C[image]3 activity in a combination of reagent sera in which C[image]3 is limiting in concentration, and the C[image]l, C[image]2 and C[image]4 are present in zero order excess. The test reagent sera, RP (complement which is depleted in properdin) and R3 (complement which is depleted in C[image]3 and properdin) were prepared from guinea pig complement. RP and R3 from both human and guinea pig sources may be used interchangeably in the properdin assay. Inulin was more satisfactory than zymosan as a properdin binding and C[image]3 inactivating agent.