['Priming of the polymorphonuclear neutrophil (PMN) response has been implicated in the activation of oxidative burst and tissue injury in patients with septic shock and acute renal failure (ARF). This study evaluated whether hemofiltration (HF) removes substances able to enhance the oxidative burst of PMNs.', 'Chemiluminescence (CL) priming activity induced by sera and ultrafiltrates of seven patients with septic shock, multiorgan dysfunction syndrome, and ARF (ARF/HF group) and of 10 uremic stable patients (Control/HF group) was evaluated on normal human PMNs stimulated with bacterial formyl-methionyl-leucyl-phenylalanine (FMLP). Patients submitted to HF were studied by determining blood and ultrafiltrate interleukin-8 (IL-8), platelet-activating factor (PAF), and CL priming activity at the beginning (T0), and after four hours (T4) of treatment.', 'Preincubation of normal human PMNs with sera and ultrafiltrates from septic patients induced a potent priming of CL activity in subsequent FMLP stimulation. In the ARF/HF group, the prefilter blood concentrations of IL-8 and CL PMN-priming activity significantly decreased during the four hours of HF treatment, with a loss of IL-8 in the ultrafiltrate of 6930 (median, range 4292 to 9282) ng per four hours. PAF detected in the ultrafiltrate and associated with the membrane (7.3 ng, range 1.45 to 9.89) was minimal. In the ARF/HF group, a significantly positive correlation between CL PMN-priming activity and IL-8 concentrations was observed. The CL priming activity in blood and ultrafiltrates was reduced to 55 and 46% by preabsorption with monoclonal antibody (mAb) anti-IL-8. In contrast, the PAF receptor antagonist WEB 2170 did not affect CL priming activity. In the control/HF group, the CL PMN-priming activity was significantly lower than in the ARF/HF group and was independent of IL-8.'] Does hemofiltration reduce the serum priming activity on neutrophil chemiluminescence in septic patients?