The haemolytic properties of the Oriental hornet venom.

: Venom from Vespa orientalis haemolyses erythrocytes of man, guinea pig, rabbit, cat, mouse and rat, but not of sheep, ox, horse and camel. The haemolytic effect was enhanced by the addition of egg yolk phospholipids. Boiling destroyed the haemolytic factor(s), but the haemolytic activity which was demonstrable after addition of phospholipids resisted boiling at pH 3.5. The haemolytic factor(s) could be removed by heparin precipitation and Amberlite adsorption and could be neutralized by rabbit anti wasp venom serum. The haemolytic factors could not be removed by dialysis. Sublytic doses of whole venom caused potassium leakage from susceptible erythrocytes and increased their osmotic fragility. It is suggested that the indirect haemolytic activity of the Oriental hornet's venom is associated with phospholipase activity, while the direct lytic activity is due to basic protein.