A human lymphokine activates macrophage C3 receptors for phagocytosis: studies using monoclonal anti-lymphokine antibodies.
We have identified a human T lymphocyte cell line, the Mo line, that constitutively elaborates a lymphokine that activates macrophage receptors for the third complement component (C3) for phagocytosis. The molecule is physically, functionally, and immunologically very similar, if not identical, to a previously characterized murine lymphokine. Both molecules were inactivated by the same physical and chemical treatments, activated macrophage C3 receptors for phagocytosis, and freed macrophage C3 receptors to move within the cell's plasma membrane. In addition, both the human and the murine products were recognized by the same monoclonal antibodies. Treatment with monoclonal antibodies abolished both the ability of lymphokine-containing supernatants to mobilize macrophage C3 receptors and the supernatants' ability to activate C3 receptor-mediated phagocytosis. The dose-response curves for both effects of the antibodies were identical, strongly suggesting that a single molecule was responsible for both effects and that the lymphokine activated marophage C3 receptors for phagocytosis by freeing the anchored receptors and allowing them to diffuse within the cell's plasma membrane. These findings strengthen the hypothesis that, for a receptor to promote phagocytosis, it must be able to diffuse within the macrophage plasma membrane.
D000818:Animals; D000911:Antibodies, Monoclonal; D002460:Cell Line; D005260:Female; D006801:Humans; D007700:Kinetics; D008214:Lymphocytes / Q000187:drug effects; D008222:Lymphokines / Q000302:isolation & purification / Q000502:physiology*; D016177:Macrophage-1 Antigen; D008264:Macrophages / Q000502:physiology*; D051379:Mice; D010587:Phagocytosis / Q000187:drug effects; D011951:Receptors, Complement / Q000187:drug effects / Q000502:physiology*; D013045:Species Specificity; D013601:T-Lymphocytes / Q000502:physiology
D000911:Antibodies, Monoclonal; D008222:Lymphokines; D016177:Macrophage-1 Antigen; D011951:Receptors, Complement