Methods for evaluation of the adhesive and phagocytic capacities of porcine granulocytes

Granulocyte function in dogs experimentally infected with a Swedish granulocytic Ehrlichia species

Granulocyte function was studied in six dogs inoculated with a Swedish granulocytic Ehrlichia species and in four control dogs. Whole blood chemiluminescence (CL) was enhanced in the dogs with granulocytic ehrlichiosis. Both CL after stimulation with zymosan and spontaneous CL was significantly increased at peak of infection compared with pre-infection levels. Ingestion of FITC-labelled serum-opsonized yeast cells was high and stable in both groups. The ingestion was lower when the yeast cells were opsonized with anti-yeast IgG. However, there was no difference between groups. The labelling intensity of anti-human CD11b, CD18 and CD32 mAb on the granulocytes in dogs with ehrlichiosis was similar to that in control dogs. The opsonic activity in serum collected at the peak of infection was not different from serum drawn prior to inoculation. Opsonic activity was investigated both by yeast cell ingestion and by chemiluminescence after stimulation with zymosan. The serum from infected dogs enhanced the respiratory burst without stimulation with zymosan of leukocytes from healthy dogs. This suggests that serum at the peak of infection contains granulocyte activators. In this study we found normal phagocytosis together with evidence of enhanced oxidative metabolism in the granulocytes from dogs with granulocytic ehrlichiosis.

Simultaneous flow cytometric measurement of Streptococcus suis phagocytosis by polymorphonuclear and mononuclear blood leukocytes

A simple flow cytometric method was used to study simultaneously the phagocytosis of Streptococcus suis serotype 2 by polymorphonuclear and mononuclear blood leukocytes from swine and humans. Using this method with a bacteria-to-leukocytes ratio of 10:1 and after 60 min of incubation, 80.2 +/- 2.8% of swine granulocytes and 77.0 +/- 2.8% of swine monocytes were shown to contain FITC-labelled S. suis serotype 2 strain 735. Using the same strain, FITC-labelled bacteria were found in 95.5 +/- 3.2% of human granulocytes and in 92.8 +/- 3.6% of human monocytes. The phagocytosis rates of avirulent and virulent strains of S. suis were not significantly different.

Dietary zinc oxide in weaned pigs--effects on performance, tissue concentrations, morphology, neutrophil functions and faecal microflora

The uptake and distribution of zinc in tissues and the effects of 2500 ppm dietary zinc oxide on health, faecal microflora, and the functions of circulating neutrophils were evaluated in weaned pigs. One group was fed a zinc supplement diet and another group was used as a control. All pigs remained healthy throughout the study, but the supplemented animals showed better performance than the controls. The serum zinc values rose rapidly. At autopsy, carried out at the age of 63 days, the zinc concentrations in liver tissue were 4.5 times higher, and in renal tissue two times higher in the supplemented group than in controls (P<0.001). Microscopic examination showed increased lipid accumulation in hepatocytes from supplemented pigs. No effect on the number of excreted Escherichia coli and enterococci per gram faeces or on the functions of circulating neutrophils was observed. Dietary supplementation with 2500 ppm ZnO for up to two weeks after weaning appears to be potentially beneficial in the prevention of postweaning diarrhoea in pigs.

Development of selected faecal microfloras and of phagocytic and killing capacity of neutrophils in young pigs

Nine healthy piglets, weaned at the age of 35 days and emanating from two litters, were studied from 7 to 63 days of age. The development of their faecal flora was analysed by bacteriological quantification of coliforms, E. coli, enterococci and Clostridium perfringens. The numbers of coliforms, E. coli and enterococci decreased from about 10(8) CFU/g faeces on day 7 to about 10(5) at the end of the study. Clostridium perfringens, with an initial value of 10(4) CFU/g faeces, was not found in any faecal sample from day 21 onwards. At each sampling occasion the similarity between the floras of different pigs were investigated by biochemical fingerprinting and calculated as correlation coefficients between metabolic fingerprints. This was performed for the coliform and the enterococcal floras. Initially, the coliform floras had a low homogeneity (rmean = 0.6), indicating large initial differences between the piglets. From day 14 post-partum until weaning the homogeneity was stable at a high level (rmean = 0.9). On day 3 post-weaning a marked decrease of the homogeneity was seen (rmean = 0.5), which later returned to the level before weaning. The enterococcal floras had a high homogeneity (rmean = 0.8-0.9) through the study and was only slightly affected by weaning. The function and development of the phagocytic and killing capacity of neutrophil granulocytes was monitored by flow cytometry and chemiluminescence. No changes in these functions were seen over time or between litters.

Flow-cytometric studies of the phagocytic capacities of equine neutrophils

Methodological aspects of flow-cytometric evaluation of the phagocytic properties of equine neutrophils were elucidated. The kinetics of attachment and ingestion were studied, and the phagocytic process was more rapidly completed when serum-opsonized yeast cells were used than with use of IgG-opsonized yeast cells. Trypan blue was successfully used to quench fluorescence of non-ingested yeast cells. There were only minor differences in the kinetics of phagocytosis between quenched and unquenched samples, indicating that attachment is rapidly followed by ingestion. Trypan blue quenching caused loss of cells with light scattering properties of granulocytes, although this did not affect the determined frequencies of truly phagocytic neutrophils. Aggregation of yeast cells proved to be a disturbance but not an obstacle to the determination of frequencies of actively phagocytic cells. Flow cytometry is well suited for studies of phagocytosis of yeast cells by equine neutrophils, and the trypan blue quenching provides a means of eliminating false-positive events due to aggregation of yeast cells. The main advantage of the flow-cytometric method is the possibility of rapid processing of a large number of samples, making the method useful for studies of herds.

Characterization of camel leukocytes by flow cytometry and microscopic evaluation of granulocyte phagocytosis of fluorescent bacteria

Peripheral blood was obtained from four lactating camels (Camelus bactrianus) and flow cytometry was used to characterize cell populations. The ability of the granulocytes to engulf fluorescent bacteria was studied in vitro using fluorescence microscopy. Three clusters of blood cells (mononuclear cells, neutrophils and eosinophils) were identified by flow cytometry and fluorescent microscopy. Milk, on the other hand, was dominated by cell fragments and no distinct cluster formation was found. The mean yield of blood granulocytes and monocytes isolated on Ficoll gradient was 92.2 +/- 5.4% and 7.9 +/- 5.7%, respectively. Cell viability was 95%. The mean percentage of phagocytic cells was 71.8 +/- 5.9% at 10 min and increased to 97.3 +/- 0.5% at 60 min when observation was terminated. The average number of bacteria per phagocyte was 8.7 +/- 2.1 and 13.1 +/- 0.9 at 10 and 60 min incubation time.