Recombinant bovine GM-CSF primes superoxide production but not degranulation induced by recombinant bovine interleukin-1β in bovine neutrophils

Bovine neutrophil activation, superoxide production, and beta-glucosaminadase release induced by various biological stimuli were examined. Platelet-activating factor (PAF) and recombinant bovine interleukin-1 beta (r-BoIL-1 beta) induced superoxide production and beta-glucosaminadase release in bovine neutrophils. When these two responses were compared, the dose requirement for maximum activation was similar for PAF (1 x 10(-6) M). However, the concentration of r-BoIL-1 beta required for the maximum degranulation (2.5 x 10(-7) M) was 100-fold higher than that for the maximum superoxide production (2.5 x 10(-9) M). Furthermore, pretreatment of cells with recombinant bovine granulocyte-macrophage colony-stimulating factor (r-BoGM-CSF) enhanced both superoxide production and beta-glucosaminidase release induced by PAF. In contrast, whereas superoxide production induced by r-BoIL-1 beta was enhanced by r-BoGM-CSF priming, beta-glucosaminidase release induced by r-BoIL-1 beta was significantly reduced by pretreatment with r-BoGM-CSF. CL 184,005, a PAF antagonist, inhibited PAF-induced glucosaminidase release and superoxide production but did not inhibit r-BoIL-1 beta-induced superoxide production and degranulation. In addition, it did not inhibit the priming effect of r-BoGM-CSF on r-BoIL-1 beta-induced superoxide production. These results suggest that (1) PAF and r-BoIL-1 beta activate bovine neutrophils by different mechanisms, (2) r-BoGM-CSF primes superoxide production and degranulation induced by PAF, (3) r-BoGM-CSF primes superoxide production but not degranulation induced by r-BoIL-1 beta, and (4) the priming effect of r-BoGM-CSF is not mediated by PAF.