Effect of pretreatment with NAP-2 or IL-8 on chemotactic migration of PMN in response to NAP-2 or IL-8. Neutrophils were pretreated with 200 nmol/L NAP-2 (•), 200 nmol/L IL-8 (▿), or left untreated (○) for 10 minutes. Washed cells were subsequently assayed for chemotaxis in response to increasing concentrations of NAP-2 (A) or IL-8 (B). Random migration of cells that received no stimulus is indicated (- - -). Data represent mean ± SD from three independent experiments.