Immunological studies of bovine platelet aggregating factor (PAF)

Abstract

A potent antiserum was produced when rabbits were immunized with a highly purified preparation of bovine platelet aggregating factor (PAF). The rabbit anti-PAF markedly inhibited the PAF activity of bovine plasma and the von Willebrand factor (vWF) activity of normal human plasma. The inhibition of bovine factor VIII coagulant activity was barely measurable. When serial dilutions of antiserum were tested against normal bovine plasma and crude PAF preparations by double immunodiffusion, rocket immunoelectrophoresis and crossed immunoelectrophoresis, precipitin bands due to contaminants were not detected. With double immunodiffusion, a single line of full immunologic identity was found with highly purified PAF and cow plasma; normal human plasma showed partial identity with the PAF arc; no precipitin arcs formed with vWD plasma. Double immuno-diffusion with crude PAF showed several precipitin bands that all fused with the single band given by highly purified PAF with the antiserum. Crossed immunoelectrophoresis of crude bovine PAF in 2% agarose showed several precipitin arcs, all immunologically related. Most of the precipitin arcs fused into a single band when the crude PAF was electrophoresed in 1% agarose. Tandem crossed immunoelectrophoresis of human plasma and PAF showed a partial relationship between PAF and human vWF, thus confirming the results from the double immunodiffusion and neutralization studies.