Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 11/14/2007
Publication Date: 12/30/2007
Citation: Karcher, E.L., Beitz, D.C., Stabel, J.R. 2008. Modulation of Cytokine Expression and Lymphocyte Subsets during the Periparturient Period in Dairy Cows Naturally Infected with Mycobacterium avium subsp. paratuberculosis. In: Proceedings of the 9th International Colloquium on Paratuberculosis, October 28th-November 2, 2007, Tsukuba, Japan. p.33-36.
Interpretive Summary: Johne's disease is a chronic, debilitating intestinal disorder in cattle,sheep and wild ruminants, characterized by diarrhea, reduced feed intake, weight loss and death. Animals usually become infected when they are young 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. During this time the animal is infected and may be shedding the organism in its feces without showing any clinical signs of disease. In addition to reduced production by these animals through reduced milk production, they also present a potential infective threat to the rest of the herd. Johne’s disease is difficult to diagnose and therefore to control. 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: The objective of this study was to evaluate cytokine gene expression and populations of lymphocyte subsets in periparturient dairy cows naturally infected with Mycobacterium avium subsp. paratuberculosis (MAP). Blood was collected from noninfected, subclinical, and clinical MAP-infected dairy cows for 3 wks pre- to 4 wk post-calving. Expression of IFN-gamma, IL-4, and IL-10 declined at calving was compared with prepartum values in both control and infected cows. PBMCs isolated from infected cows had higher secretion of IFN-gamma, IL-10, and TGF-ß in the postpartum period compared with control cows. Flow cytometric analysis revealed that 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. 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 data suggest that parturition is a very dynamic time period for host immunity, with potential for altered immunity to hinder the ability of dairy cows to thwart infectious diseases.