LEUKOCYTE MIGRATION-INHIBITORY FACTOR - SERINE ESTERASE RELEASED BY STIMULATED HUMAN LYMPHOCYTES - KINETIC-ANALYSIS AND INHIBITION BY CYCLIC-GMP

Lymphocytes, stimulated with concanavalin A, release small amounts of non-immunoglobulin, highly reactive proteins called lymphokines. One of these, a serine esterase termed leukocyte migration inhibitory factor according to its function in vitro, is found in supernatants of stimulated human lymphocytes at concentrations less than 1 ng/ml. The esterase was purified in good yield and its esterolytic activity was measured by a sensitive radioenzymic assay. The kinetics of the esterolytic activity were studied and the effect of various nucleotides examined. Competitive inhibition of esterolysis was seen with cyclic[c]GMP at concentrations down to 10-7 M, and with 2'',3''-cCMP at a concentration of 10-3 M. A role of this esterase as a mediator acting upon polymorphonuclear leukocytes and as an intracellular regulator of lymphocyte activation is discussed.