Abstract
The study aimed to investigate the formation of immunological memory to Salmonella antigens in cows using different phenotypes of T-lymphocyte populations. The study was conducted on farms in Kazakhstan and Latvia. As part of the study, blood samples were collected from cows vaccinated against Salmonella to analyse T-lymphocyte phenotypes. A comparative study of different phenotypes of T-cell populations, including CD4+, CD8+, γδ T-cells and effector T-cells (CD45RA+ and CD45RA-), was conducted to assess their role in the formation of immunological memory. Flow cytometry and enzyme-linked immunosorbent assay (ELISA) were used to quantify T-cell populations and levels of specific antibodies. The main results showed that vaccination causes a significant increase in the population of CD4+ and CD8+ T-lymphocytes, which correlates with an increase in the level of specific antibodies to Salmonella antigens. The γδ T-cell population also showed significant activation, indicating their potential role in the formation of an immune response to Salmonella. Particular attention was devoted to effector cells of T-lymphocytes: CD45RA+ cells were actively involved in the primary immune response to Salmonella antigens, while CD45RA cells showed high activity during repeated exposure to the antigen, indicating their key role in maintaining longterm immunological memory. Comparative analysis of data from Kazakhstan and Latvia showed similar trends, indicating the universality of the observed immunological mechanisms. These findings highlight the importance of including different T-cell phenotypes in vaccination programmes to ensure more effective immunological memory in cows. Thus, this study provides valuable data on the role of different T-lymphocyte populations in the formation of immunological memory to Salmonella antigens in cows, which may contribute to the development of more effective vaccine programmes and improve the health and productivity of livestock in the regions of Kazakhstan and Latvia