Submitted to: Veterinary Immunology and Immunopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/11/2008
Publication Date: 1/19/2008
Citation: Karcher, E.L., Beitz, D.C., Stabel, J.R. 2008. Parturition Invokes Changes in Peripheral blood Mononuclear Cell Populations in Holstein Dairy Cows Naturally Infected with Mycobacterium avium subsp. paratuberculosis. Veterinary Immunology and Immunopathology. 124(1-2):50-62. Interpretive Summary: Johne's disease is a chronic, debilitating intestinal disorder in cattle characterized by diarrhea, reduced feed intake, weight loss and death. Cattle usually become infected as young calves by ingesting feces containing the causative bacteria. However, symptoms of disease do not usually present themselves until the animals reach 3 to 5 years of age or even older. Clinical signs of disease may be precipitated by stressors such as parturition, heavy lactation, concomitant viral or bacterial infections, and malnutrition. It is well known that parturition causes cows to become immunosuppressed and makes them more susceptible to infections such as mastitis and metritis as well as other viral and bacterial pathogens. The present study was designed to evaluate the effects of the periparturient period on host immunity in healthy cows and naturally infected cows with paratuberculosis. Parturition decreased host immunity in cows regardless of infection status. In addition, paratuberculosis resulted in changes in host immunity compared to healthy noninfected cows. These results suggest that the periparturient period is a highly significant period for the dairy cow and may result in increased susceptibility to infectious diseases.
Technical Abstract: Johne’s disease, caused by Mycobacterium avium subsp. paratuberculosis (MAP), is estimated to infect more than 22% of US dairy herds. Once infected, cows may remain in the asymptomatic subclinical state until a period of stress, such as parturition. Parturition has a major impact on the number of T and B-cells, components of the adaptive immune system, and the number of monocyte/macrophages, which are effectors of the innate immune system. Therefore, the objective of this study was to determine the percentages of CD4+, CD8+, and gamma-delta T-cells, B-cells, and monocytes in the peripheral blood of dairy cows naturally infected with MAP during the periparturient period as compared with healthy control cows. In addition, cell populations were further delineated by staining for CD5, a marker for T- and B-cell activation. Twenty-one multiparous and two primiparous Holstein cows were grouped according to infection status. Groups consisted of 5 healthy control cows, 14 subclinical, and 4 clinical cows naturally infected with MAP. Blood was collected from jugular vein at -21, -14, -7, +1, +7, +14, and +28 days relative to calving, and peripheral blood mononuclear cells (PBMCs) were isolated. Cells were incubated for either 24 h or 7 d. At d 7, cultures were divided into control and treated samples; treated were exposed to live MAP, and both were incubated for an additional 24 h. At both time points, fluorescent antibody labeling of lymphocyte subsets and monocytes was conducted and analyzed with flow cytometry. Results show that after 24 h of incubation, subclinical cows expressed a greater percentage of both CD8+ and gamma-delta T-cells compared with the clinical cows. The percentage of CD4+ T-cells increased in clinical cows as parturition approached. During the postpartum period, clinical cows had a greater CD4+ to CD8+ ratio compared with subclinical and control cows. In 8 d control PBMCs, clinical cows had greater percentages of CD14+ cells compared with subclinical cows. When stimulated with live MAP, there was no effect of infection group or parturition on percentage of cells expressed. In 24 h PBMCs, clinical cows expressed lower percentages of CD4+/CD5bright and CD8+/CD5bright compared with control cows, but greater percentages of CD5dim cells for all lymphocyte subsets. These results suggest changes in the percentages of lymphocyte subsets, monocytes, and CD5 markers are modulated by both infection status of the animal and the periparturient period.