Measurement of Sarcophaga peregrina lectin under various physiological conditions by radioimmunoassay.

Lectin induced in the hemolymph of Sarcophaga peregrina (flesh fly) larvae on injury of the body wall or on pupation was studied further by radioimmunoassay, focusing on the interaction between the lectin and hemocytes. It was found that the amount of lectin on the surface of hemocytes prepared from injured larvae increased with time after injury of the body wall. Radioiodinated lectin could bind to hemocytes prepared from injured larvae more effectively than those from normal larvae, indicating a difference in the affinities to lectin of hemocytes from these two sources. The lectin was found to be synthesized in the fat-body and then secreted into the hemolymph both on injury of the body wall and on pupation. A significant level of lectin was maintained in pupae during the entire pupal stage, but it decreased rapidly before emergence, and no lectin was found in newly emerged flies. Since the lectin greatly activated the activity of mouse bone marrow cells to kill Candida parapsilosis cells, the biological significance of humoral lectin in the defense mechanism was discussed from the ontogenic viewpoint.