Kinetic studies of phagocytosis of IgG-coated latex particles with a thrombocyte counter.

An assay was developed making possible the measurement of the initial rate of phagocytosis of IgG-coated polyvinyl toluene latex particles by human leukocytes. With the use of the volume-discrimating ability of a Trombo-Counter, the small latex particles could be selectively counted, but cells and internalized particles were not counted. The phagocytic uptake was greatley enhanced by an IgG coating of the particles as compared to the uptake of uncoated or albumin-coated particles. An almost complete inhibition of particle uptake was obtained at ice-bath temperature and in the presence of N-ethyl maleimide. Heat-inactivated serum and monomeric IgG inhibited the phagocytic reaction. In the presence of fresh serum a stimulatory effect on the final phagocytic capacity was noticed, but the initial rate of particle uptake varied depending on the preincubation time of particles with serum.