A human monocyte system for the assay of plasma opsonins

Previous bioassays for studying the opsonic regulation of the monocyte-macrophage system are subject to a variety of serious disadvantages which limit their value. An assay system is described which avoids many of these pitfalls and is applicable to the rapid assay of large numbers of samples. Human monocytes were isolated from peripheral blood and Saccharomyces cerevisiae used as the target particle. Particle ingestion was assessed using an electronic particle size analyzer and a close correlation was shown between this assay and a visual assessment of ingested micro-organisms.