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Comparison of white blood cell phagocytic efficiency in two genotypes of Katahdin sheep
The production and deployment of phagocytic cells are central functions of the hematopoietic system. Neutrophils, the most abundant type of white blood cells in mammals, are an essential part of the innate immunity. The objective of this study is to compare the phagocytic efficiency of neutrophils in two genotypes of footrot resistant and susceptible Katahdin sheep.
Fourteen Katahdin ewes, 7 in each of high resistant footrot gene markers (HR) and low resistance (LR) were selected and blood sampled, weekly for 8 weeks. Blood samples were collected in vacutainer tubes (2 x 10 ml) contained EDTA. Blood smears were made on glass slides to determine the percentage of neutrophils in whole blood. Neutrophils were isolated using a Percoll gradient technique, and stained with 0.8 mM Trypan Blue to determine the percentage of viable cells. Subsequently, 1 ml of freshly isolated neutrophils was inoculated with 1 ml of Lactobacillus casei (2 x 10 7/ ml) in PBS and incubated with rotation at 37ºC for three time periods at 20 minutes, 40 minutes and one hour. Control samples were incubated in PBS with neutrophils alone to account for bacterial growth during the assay. At specific intervals of 20, 40, and 60 minutes the number of surviving bacteria in the supernatant (extracellular) was determined by culture plate colony counting to estimate the phagocytic efficiency of the neutrophils. The data were analyzed by using mixed model procedures of SAS and P < 0.05 was considered as significant.
The average viability of extracted neutrophils was 95% in each individual specimen at inoculation. The percentage of neutrophils in whole blood was not significantly different (P = 0.57) in HR vs. LR genotypes. There were no significant differences (P = 0.63) among the numbers of bacterial colonies after addition of neutrophil and incubation periods in HR vs. LR genotypes. The number of bacterial colonies significantly decreased after 20, 40, and 60 minutes of incubation (P < 0.001). The interaction of time and gene marker groups was not significant (P = 0.23). No bacterial colony growth was observed in control samples. There is no difference in phagocytic efficiency of the white blood cells in footrot resistant and susceptible genotypes of Katahdin sheep.
Keywords: Neutrophil, Phagocytic efficiency, Sheep