In vitro experiments were conducted to determine the influence of source of neutrophils (individual calves) and calf age on phagocytic and oxidative burst activities of neutrophils isolated from 106 clinically healthy Holstein-Friesian calves. Calves were categorised by age into four groups: group A, 3-7 days; group B, 8-14 days; group C, 15-21 days or group D, 22-31 days. Neutrophils were isolated (purity > 90%, viability > 97%) from EDTA-anticoagulated blood. Aliquots of 2 x 106 neutrophils were incubated at 37°C for 30 min with fluorescein-labelled Escherichia coli 0111:B4J5, E. coli 0157:H7 and Salmonella dublin, and with pooled bovine serum as the opsonin. Percentage phagocytosis and averaged number of intracellular bacteria per neutrophil were evaluated by fluorescence microscopy. Mean channel intensity was determined by flow cytometry using dichlorofluorescein diacetate and phorbol myristate acetate to evaluate H2O2 production, a measure of oxidative burst. Significant (p < 0.05) variation in neutrophil phagocytic activity for each bacterial type was attributed mainly to the source of neutrophils and partially to the influence of age. In the phagocytic assays, the percentages of variation due to the cell source were 33.3%, 38.7% and 20.9% for E. coli 0111:B4 J5, E. coli 0157:H7, and S. dublin, respectively. The respective percentages of variation due to age were 17.4%, 7.7% and 24.5%. Similarly for H2O2 production assays, percentages of variation due to cell source and age were 69.2% and 8.1%, respectively. In general, significant variation among the four age-specific groups was found for percentage phagocytic, average number of intracellular bacteria per neutrophil and in H2O2 production. Differences were particularly evident between groups A and B, and between groups B and D. These results support the concept of functional heterogeneity of neutrophils among neonatal calves.
|Original language||English (US)|
|Number of pages||7|
|Journal||Comparative Haematology International|
|State||Published - 1997|
- Escherichia coli 0157:H7
- Salmonella dublin
ASJC Scopus subject areas