Biologic Properties of Polynucleotides. IV. Studies on the Mechanism of Complement Inhibition by Polyinosinic Acid Together with Observations on the In Vivo Effect of Polyinosinic Acid on Complement Activity*

Abstract

The mechanism of the anticomplementary activity of polyinosinic acid was investigated by its effect on the behavior of sensitized sheep erythrocyte-complement intermediates. Polyinosinic acid inhibited selectively the first component of complement (C[image]1). In contrast to other inhibitors of C[image]1, polyinosinic acid had no effect on C[image]1 esterase activity. The possibility that the anticomplementary properties of polyinosinic acid are mediated through some interaction with 7 S gamma globulin has been excluded with reasonable certainty. When injected intravenously into Wistar rats, polyinosinic acid is capable of precipitously lowering complement activity in vivo.