Phagocytosis of unopsonized zymosan by human monocyte-derived macrophages: maturation and inhibition by mannan.

Human monocyte-derived macrophages phagocytosed zymosan in the absence of serum opsonins. The capacity to ingest zymosan developed after the cells were cultured in vitro for 3 days and was inhibited completely by mannan. We conclude that human monocyte-derived macrophages phagocytose unopsonized zymosan predominantly via mannose receptors.