Inhibition of the classical and alternative pathways of human and guinea pig complement by pyran copolymer

The ability of pyran copolymer to interact with the classical and alternative pathways of complement was assessed in human and C4-deficient guinea pig serum. Pyran induced a dose-dependent inhibition of hemolytic activity in both serum systems. Immuno-electrophoretic analysis of pyran-treated human serum revealed that C3 was not cleaved. Factor B was altered into a more anionic mobility which was not similar to biologically cleaved Ba or Bb fragments. Pyran-treated serum was unable to lyse antibody-coated erythrocytes (EA or EA coated with C1 and C4 and EA coated with C1, C4 and C2. Pretreatment of serum with ethylenediaminetetraacetic acid did not prevent inhibition of hemolytic activity by pyran. Cobra venom factor did not cleave C3 in the presence of pyran. These data indicate that pyran does not activate complement by standard mechanisms but does inhibit one or more of its components.