Mechanism of priming of human neutrophils by a soluble lymphoblastoid cell factor

Treatment of human neutrophils (PMN) with a cytokine-like factor in the supernatants of human lymphoblastoid cells (Raji) increased the random mobility and enhanced the migration of treated cells in response to other chemoattractants nearly 21/2-fold, although the supernatant itself was not a chemoattractant. Supernatant treatment also increased the adherence of bacteria threefold and the bacterial killing fourfold compared with PMN treated with control media. In examining the metabolic basis for the enhanced bactericidal ability, we observed a significant increase in spontaneous hexose monophosphate shunt activity of Raji cell supernatant (RS)-treated neutrophils even in the absence of additional stimuli. RS-treated PMN also had significantly enhanced production of superoxide anion and chemiluminescence response upon subsequent stimulation with a variety of soluble and particulate stimuli. Unlike other agents that prime neutrophil activation, however, the factor(s) in RS did not cause degranulation. It also differed in its ability to progressively enhance PMN functions with a longer period of preincubation (up to 3 hr). These data suggest that the RS factor(s) primes neutrophils by a unique mechanism. The neutrophil-enhancing activities of RS, which are the opposite of those activities described for leukocyte inhibitory factor, eluted off a Sephacryl S-200 column at approximately 30,000 m.w. This factor expands the relationship between neutrophils and lymphocytes, and may be a useful agent to provide valuable insights into the mechanism of respiratory burst activation and regulation.