TUMOR-NECROSIS-FACTOR PRIMES NEUTROPHILS BY SHORTENING THE LAG PERIOD OF THE RESPIRATORY BURST

Pretreatment of neutrophils (PMNs) with low-dose tumor necrosis factor (TNF) enhances their capacity to produce oxidant radicals after stimulation with a variety of agents ('priming'). We used a continuous cytochrome C assay to investigate the superoxide production by human PMNs primed with TNF and subsequently stimulated with phorbol myristate acetate (PMA). There was no difference in the maximum rate of superoxide production by primed and unprimed PMNs stimulated with either high (2 x 10-6M) or low levels of PMA (2 x 10-8M). Following stimulation with high levels of PMA, primed PMNs demonstrated a significantly shorter lag period than unprimed cells (103.3 ± 14.4 vs. 142.1 ± 21.7 seconds) and larger amounts of superoxide generated in the intervals between 100 seconds (3.1 ± 0.5 vs. 1.7 ± 0.3 nmol/106 PMNs) and 300 seconds (14.9 ± 1.2 vs. 12.2 ± 1.1). Primed cells stimulated with low levels of PMA (2 x 10-8M) displayed a significantly shorter lag period (1225.8 ± 96.8 vs. 1573.8 ± 74.3 seconds) and a greater production of superoxide between 1300 seconds (5.4 ± 0.9 vs. 3.0 ± 0.4 nmol/106PMNs) and 1900 seconds (25.7 ± 4.3 vs. 14.9 ± 2.4) than unprimed cells. These results indicate that priming of PMNs with TNF increases superoxide production during the early phase of the respiratory burst through a shortening of the post-stimulation lag period.