Partial characterization of leukocyte inhibitory factor by concanavalin A-stimulated human lymphocytes (LIF Con A)

Leukocyte inhibitory factor (LIF) obtained from normal human lymphocytes stimulated by Concanavalin A was characterized by Sephadex gel filtration, disc electrophoresis, isopycnic centrifugation, enzymatic treatment and by immunoabsorbent studies. LIF activity was found after Sephadex G-100 gel filtration in a fraction containing molecules having the size of albumin (68,000 daltons). This is the same region were LIF activity derived from antigen-stimulated lymphocytes has previously been found to elute. On disc gel electrophoresis at pH 9.1, peak LIF activity was eluted from the acrylamide gel fraction containing molecules that migrate with albumin. In isopycnic centrifugation studies, human LIF was shown to have a buoyant density similar to that of pure protein. Human LIF was inactivated by treatment with chymotrypsin but not by neuraminidase treatment. LIF activity could not be removed by incubating the material on columns containing Sepharose 6b coupled with anti-human serum albumin or anti-Fab. The characteristics of human LIF and migration inhibitory factor were compared.