Abstract
The study aimed to investigate how the number of effector memory cells changes under the influence of a Salmonella vaccine antigen in cows. A homogeneous group of 100 Holstein-Friesian cows, kept under the same conditions, had blood samples taken. The blood was collected at four time points: before the first vaccination, and 7, 45, and 56 days after. The cows also received a booster vaccination on days 8-10. They were immunised with a polyvalent vaccine against livestock salmonellosis in Kazakhstan. Blood was separated into plasma and cellular fractions by centrifugation at 1,500 rpm for 10 minutes. The cellular fraction was then analysed by flow cytometry to determine the number of CD4+, CD8+, and γδ T-cell subpopulations at the four time points: before vaccination, and at 7-, 45-, and 56-days post-vaccination. Analysis of over 10,000 cells from each sample was conducted using FlowJo software. The data showed that the population of CD4+ and CD8+ T-lymphocytes and γδ T-cells increased 1.5 times by day 7 after the initial vaccination. The cows then received a booster dose on days 8-10, and by day 45 after the first vaccination, the CD4+ and CD8+ T-lymphocyte and γδ T-cell populations had increased threefold. CD45RA+ T-lymphocytes and γδ T-cells demonstrated a steady increase by day 45, followed by a decline in the numbers of T-cells across all phylogenetic groups. Thus, it can be concluded that the primary vaccination stimulates the development of long-term immune memory, while the booster dose triples the number of CD4+, CD8+, and γδ T-cell subpopulations. The findings provide insights into the mechanism of adaptive immunity formation in cows against salmonellosis through the use of effector memory cells and may be applied in developing vaccination strategies for cattle