Human leukocyte migration inhibition factor (LIF) increases polymorphonuclear cell endocytosis.

We prepared supernatants of Concanavalin-A activated human lymphocytes containing high titers of leukocyte migration inhibition factor (LIF). A pool of these supernatants was filtered thorough sephadex 6-100 as well as a pool of supernatants from parallel non activated cultures. A migration assay was carried out for each activated fraction, using as control migration the same fraction from non activated supernatants. In this way we found a fraction from activated supernatants with high LIF activity. We assayed the effect of this LIF containing fraction on a yeast endocytosis assay by polymorphonuclear (PMN) cells. We found that the LIF containing fraction increased the number of endocytic PMN in about 80%. This effect was absent from control supernatant and from other fractions from activated supernatant but without LIF activity. The LIF containing fraction did not increase the average number of endocytosed yeast per cell nor the ability to reduce NBT. The endocytosis enhancing effect was blocked by the specific LIF blocker N-acetyl-D-glucosamine. We conclude that LIF can increase the endocytic activity of PMN cells.