Rat and human polymorphonuclear leukocyte derived lymphocyte stimulatory factors

The kinetic release of lymphocyte activating factors by inflammatory rat polymorphonuclear leukocytes (PMNs) into culture fluid was studied. PMNs, collected from the pleural cavity of rats 4 hours after injection of either calcium pyrophosphate (CaPP) or normal plasma, released into the supernatant culture fluid, factors which enhanced the phytohaemagglutinin-induced proliferative response of normal lymph node cells or thymocytes, the optimal culture time being 24 hours. A major portion of these lymphocyte activating factors was found in the ultrafiltrates (less than 10,000 daltons) of PMN supernatants. The activities in both unfractionated supernatant and the ultrafiltrate were significantly enhanced if PMNs were exposed to Concanavalin A (Con A) or inflammatory exudate prior to supernatant production. Also, these were not species specific as rat PMN supernatant can stimulate the phytohaemagglutinin-induced response of human lymphocytes and, conversely, human PMN factors can stimulate rat thymocytes.