Inflammatory Cytokines and Antigen-Responsive Mononuclear Cells in Peripheral Blood of Cattle Infected with Salmonella Takoradi

Abstract

To determine the immunological response in lactating dairy cows infected with Salmonella (S.) Takoradi, the relationships among distributions of peripheral blood mononuclear cell (PBMC) subpopulations, endotoxin concentrations and dynamics of inflammatory cytokines in blood were investigated. The ratio of CD4⁺ T cells to CD8⁺ T cells was significantly lower in the affected cattle than in the control cattle (p<0.05) to decrease in the number of CD4⁺ T cells in the infected cattle. In contrast, the numbers of γδ-T cells, MHC class II-positive cells were significantly higher in the affected cattle than in the control cattle (p<0.01 respectively). Endotoxemia was found in all but one of the affected cattle. Serum IL-1 and IL-6 bioactivities were significantly higher in the affected cattle than in the control cattle (IL-1, p<0.05; IL-6, p<0.01). Serum TNF-α activities and levels were not detected in the control and affected cattle. The activities of proinflammatory cytokines determined by the bioassay are important to the relationships between concentration of endotoxin, cytokines and clinical signs, such as leukocytosis, leukopenia, fever or bacterial shedding. Serum IL-2 levels were lower in the affected cattle than in the control cattle. Serum IFN-γ was not detected in the affected cattle except one. These results by the ELISA seemed to reflect the condition of subpopulation in the PBMCs from the shedding cattle. The present results suggest that cellular immunity is suppressed while the humoral immunity is activated in acute bovine salmonellosis.