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

Bovine neutrophil activation, superoxide production, and β‐glucosaminadase release induced by various biological stimuli were examined. Plateletactivating factor (PAF) and recombinant bovine interleukin‐1 β (r‐BoIL‐1β) induced superoxide production and β ‐glucosaminadase release in bovine neutrophils. When these two responses were compared, the dose requirement for maximum activation was similar for PAF (1 × 10 −6 M). However, the concentration of r‐BoIL‐Ι β required for the maximum degranulation (2.5 × 10 −7 M) was 100‐fold higher than that for the maximum superoxide production (2.5 × 10‐ 9 M). Furthermore, pretreatment of cells with recombinant bovine granulocyte‐ macrophage colony‐stimulating factor (r‐BoGM‐CSF) enhanced both superoxide production and β ‐glucosaminidase release induced by PAF. In contrast, whereas superoxide production induced by r‐BoIL‐1 β was enhanced by r‐ BoGM‐CSF priming, β ‐glucosaminidase release induced by r‐BoIL‐l β 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‐l β ‐in‐ duced superoxide production and degranulation. In addition, it did not inhibit the priming effect of r‐BoGM‐ GSF on r‐BoIL‐l β ‐induced superoxide production. These results suggest that (1) PAF and r‐BoIL‐1 β 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‐l β , and (4) the priming effect of r‐BoGM‐CSF is not mediated by PAF.