Neutrophil product with lymphocyte activating factor activity.

Lymphocyte activating factor (LAF) is a monocyte derived product which has the ability to enhance the proliferative response of murine thymocytes to the T cell mitogen concanavalin A (Con A). In this report, we have demonstrated that supernatants from normal human polymorphonuclear cells (PMNs) and from granules obtained from PMNs exhibit activity identical to LAF when tested against mouse thymocytes. Our results suggest that PMNs may release factors essential for T cell activation and thus, like monocytes, may serve as important accessory cells in the development of T cell-dependent immunity.