Isolation and characterization of Guinea pig properidin.

Guinea pig properdin was purified to homogeneity by employing as an assay during isolation its capacity to augment the hemolytic activity of a heterologous human C3b-dependent C3 convertase, C3B. The purified protein elicited a monospecific antibody response in a rabbit. The antiserum, by immunodiffusion, gave a reaction of identity between a protein in whole guinea pig serum and the immunogen. A solid phase immunoadsorbent prepared with the antiserum removed properdin function from the purified protein. The purified guinea pig protein exhibited the classical properdin function of reconstituting a human RP for zymosan-induced C3 inactivation. The guinea pig properdin also agglutinated red cell intermediates bearing either guinea pig or human C3b and retarded the decay of homologous C3 convertase, C3B. These activities are the same as those observed for purified human properdin and validate the amplification function of properdin on terminal component activation in a second species.