Short communication: Effect of granulocyte-macrophage colony-stimulating factor on neonatal calf peripheral blood neutrophil function in vitro

摘要

Neutrophils are innate immunity cells that representthe first line of cellular defense against invading pathogens.Dairy calves, however, experience neutrophildysfunction during the first weeks of age, contributingto increased disease susceptibility during this period.Granulocyte-macrophage colony-stimulating factor(GM-CSF) is a cytokine that improves neutrophilfunction in neonates of other species and mature cows.However, its capability to improve neonatal calf neutrophilfunction is unknown. Therefore, our objectivewas to evaluate the effect of GM-CSF on the functionalcapabilities of neutrophils of neonatal calves in vitro.We hypothesized that supplementation of neonatalneutrophils with GM-CSF would increase microbicidalfunctions to levels comparable with those of matureimmunocompetent cattle. For this, we isolated bloodneutrophils from 12 healthy 2- to 3-d-old Holsteincalves, and neutrophils from 6 mid-lactation Holsteincows were used as a reference of robust neutrophilfunction. Subsequently, neutrophils from both calvesand cattle were incubated for 9 h with 4 concentrations(0, 0.005, 0.05, or 0.5 μg/mL) of GM-CSF, andmicrobicidal function of neutrophils was assessed interms of phagocytosis, respiratory burst, myeloperoxidase(MPO) activity, and extracellular trap formation.Mixed models with Tukey pairwise comparisons wereused to identify differences among treatment and agegroups. Supplementation of GM-CSF in vitro increasedphagocytosis and MPO activity of calf and cow neutrophils,although not in a concentration-dependent manner.Respiratory burst and extracellular trap formationwere not affected by GM-CSF supplementation. All themicrobicidal capacity functions assessed were lower inneutrophils from calves, but supplementation with GMCSFincreased phagocytosis and MPO activity of calfneutrophils to levels comparable with unsupplementedcow neutrophils. Collectively, our results demonstratedthat in vitro supplementation of calf neutrophils withGM-CSF enhanced some functional microbicidal capabilitiesto levels comparable with immunocompetentcattle. Hence, it may be possible to augment the functionalcapacity of calf neutrophils in vivo through thetherapeutic application of GM-CSF and consequentlyenhance calves’ resistance to infections. This should betested in future in vivo studies.