Activation of neutrophilic granulocytes by products of human lymphocytes.

Materials produced by stimulated primary cultures of human lymphocytes and by a continuous human lymphoid cell line, RPMI 1788, were tested for granulocyte phagocytosis promoting activity. Blood lymphocytes of healthy donors were stimulated with tuberculin (PPD) or concanavalin A (con A) and the culture fluids collected after 3 days of in vitro incubation. Fluids of the lymphoid cell line were collected from 2-day-old cultures. All three kinds of preparations were found to induce a significant increase in neutrophilic granulocyte phagocytic activity. Studies on the kinetics of granulocyte activation revealed that it is a relatively rapid process, being maximal within 60–120 min. This is in contrast to the considerably slower activation of monocytes in a comparable system. Intracutaneous inoculation of the active materials in human volunteers resulted in reactions that grossly and histologically resembled accelerated delayed type hypersensitivity reactions.