Partial characterization of a novel chemotactic factor produced by macrophages.

The production of substances by lymphocytes or macrophages under activation involved in regulating immune responses, has led us to study a new macrophage factor with chemotactic activity for lymphocytes. This factor is produced early in the immune response activation (6 hours, in vitro) by peritoneal exudate adherent cells under stimulation with sheep red blood cells (SRBC) and it induces lymphocyte chemotaxis. We have confirmed this factor is a polypeptide susceptible to proteolytic digestion. Besides, its receptor on T cells requires the presence of glycosylated sites, specially sialic acid. It was determined that such a chemotactic factor was not interleukin-1, a well-characterized mitogenic and chemotactic substance for T lymphocytes.