Effects of dialyzable leukocyte extracts (DLEs) with transfer factor activity on leukocyte migration in vitro. III. Characterization of the antigen-independent migration inhibition factor in DLEs as a neutrophil immobilizing factor.

In earlier evaluations of the agarose LMI assay as an in vitro test for studying the nature and mechanism of action of TF, we reported the existence of a component in human DLEs which caused noncytotoxic inhibition of the random migration of human PMNs. The LMI was not dependent on the stimulation of viable mononuclear leukocytes by antigen or mitogen to effect the release of mediators of cellular immunity such as LIF; rather, the LMI was promoted by the direct action of a preexisting component in DLEs on PMNs. We now present evidence that this "antigen-independent" LMI activity in DLE'S is similar to a NIF shown previously by Goetzl and co-workers to be present in acid extracts of leukocytes and to be released by phagocytosing PMNs. The comparison is drawn from several parameters: (1) cellular origin, (2) molecular weight, (3) target cell, (4) susceptibility to inactivation by heating or by incubation with pronase, trypsin, or chymotrypsin, and (5) ability to cause noncytotoxic inhibition of random migration or chemotaxis of PMNs.