Dialyzable Factor in Normal Allantoic Fluid Inhibiting Hemagglutination Patterns with Newcastle Disease Virus.

Abstract
A dialyzable factor, present in chick embryo allantoic fluid suspensions of Newcastle disease virus, (NDV) as well as in normal allantoic fluid, inhibited the formation of hemagglutination patterns by certain strains of NDV. The inhibiting activity was more effective at 4[degree] C than at 25[degree] C but the inhibitor resisted heating at 100[degree] C for 30 minutes. It was not destroyed by receptor destroying enzyme. Within the limits of the procedures employed the inhibiting factor showed no capacity for permanently combining with or changing any of the components of the NDV hemagglutination system studied.