Lack of specificity of the C3-opsonized zymosan reagent for the assay of membrane complement receptors

C3-opsonized zymosan particles (C3-zymosan) have been utilized as reagents for detection of C3 receptor bearing cells. However, in this communication we present evidence that C3-zymosan particles are not useful for this purpose in some species with certain macrophage populations because of non-specific binding of unopsonized zymosan.