In vitro phagocytosis by amoebocytes from the haemolymph of Helix aspersa (Müller). I. Evidence for opsonic factor(s) in serum.

phagocytosis of foreign particles by amoebocytes from the haemolymph of (Müller) was studied. Results showed the presence of an opsonin in serum. This opsonic effect of serum is due to the adsorption of serum component(s) on to the foreign particles. No phagocytosis occurs in the absence of these factors. There was some degree of specificity of the opsonin for two different foreign particles: formalized yeast cells () and formalized sheep red blood cells.