Related Experiment Videos
Polymorphonuclear neutrophil leukocyte function in clinical bovine patients and in cows with or without
K L Anderson1, L A Smith, F J DeGraves
1Department of Food Animal and Equine Medicine, College of Veterinary Medicine, North Carolina State University, Raleigh 27606.
Abstract:
A fluorochrome microassay was used to investigate peripheral blood polymorphonuclear leukocyte (PMNL) function in cattle. Glass-adherent PMNL were reacted with Staphylococcus aureus preincubated in 20% bovine serum for 30, 60 and 90 min. Coverslips were stained with acridine orange (AO) followed by crystal violet to quench extracellular bacterial fluorescence. PMNL function was evaluated by counting the number of dead (stained red with AO) and live (stained green with AO) S. aureus contained within 100 PMNL. A phagocytic index was calculated as the average number of bacteria contained within PMNL. The percentage killing of S. aureus was calculated from the average proportion of S. aureus within PMNL that were dead. Six clinically normal Holstein calves, 3-4 months of age, were sampled on 6 consecutive days. PMNL phagocytosis and killing did not vary significantly (p greater than 0.05) among repeated samplings per calf. PMNL function increased with increasing time of incubation of PMNL with S. aureus. Means (+/- SD) for percentage killing were 46.7 +/- 13.1, 57.4 +/- 11.6, and 62.1 +/- 9.8% for 30, 60 and 90 min of reaction, respectively. Means (+/- SD) for the phagocytic index were 2.9 +/- 0.8, 3.6 +/- 1.0, and 4.2 +/- 1.1 bacteria/PMNL for 30, 60 and 90 min of reaction, respectively. PMNL function was determined in 30 normal cattle of various breeds, age and sex, and these values were pooled to provide normal values for PMNL function. When values for bovine clinical patients (n = 25) with various diagnoses were compared with normal values (defined by the mean +/- 2SD for the 30 normal cattle) for PMNL function, only one patient was observed to exhibit PMNL hypofunction. A cow with disseminated intravascular coagulation in association with peracute coliform mastitis exhibited decreased PMNL killing capacity. Abnormal PMNL function was uncommon in the hospital population studied. Peripheral blood PMNL function was evaluated in lactating Holstein cows with (n = 15) or without (n = 15) chronic subclinical S. aureus mastitis. There was no significant (p greater than 0.05) difference in PMNL function among these cows.
Insights
This study assessed polymorphonuclear leukocyte (PMNL) function in cattle using a fluorochrome microassay. PMNL phagocytosis and killing of Staphylococcus aureus increased with incubation time, and abnormal function was rare in clinical patients.
Area of Science:
- Veterinary Immunology
- Bovine Health
- Infectious Disease
Background:
- Peripheral blood polymorphonuclear leukocytes (PMNL) are crucial for innate immunity in cattle.
- Assessing PMNL function is vital for understanding bovine immune response and disease susceptibility.
- Standardized methods are needed to evaluate PMNL phagocytic and bactericidal capacities.
Purpose of the Study:
- To establish a fluorochrome microassay for evaluating bovine peripheral blood PMNL function.
- To determine normal ranges for PMNL phagocytosis and killing of Staphylococcus aureus in cattle.
- To assess PMNL function in cattle with various clinical conditions and subclinical mastitis.
Main Methods:
- A fluorochrome microassay using acridine orange staining was employed to quantify PMNL interaction with Staphylococcus aureus.
- PMNL phagocytic index and percentage of S. aureus killing were calculated after 30, 60, and 90 minutes of incubation.
- Normal PMNL function values were established from 30 healthy cattle and compared to clinical cases (n=25) and cows with subclinical mastitis (n=30).
Main Results:
- PMNL phagocytosis and killing of S. aureus significantly increased with longer incubation times (30, 60, 90 min).
- Repeated sampling in calves showed no significant variation in PMNL function.
- Only one of 25 clinical patients exhibited hypofunction; chronic subclinical mastitis did not significantly alter PMNL function.
Conclusions:
- The fluorochrome microassay is a reliable method for assessing bovine PMNL function.
- Abnormal PMNL function is uncommon in cattle, even in the presence of various diseases.
- Chronic subclinical Staphylococcus aureus mastitis did not impair peripheral blood PMNL function in lactating cows.