Submitted to: Veterinary Immunology and Immunopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/3/2008
Publication Date: 12/1/2008
Citation: Stabel, J.R., Khalifeh, M.S. 2008. Differential Expression of CD5 on B Lymphocytes in Cattle Infected with Mycobacterium avium subsp. paratuberculosis. Veterinary Immunology and Immunopathology. 126(3-4):211-219. 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. 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 milk production by these animals, they also present a potential infective threat to the rest of the herd. Johne’s disease is difficult to diagnose and therefore to control. Development of accurate and sensitive diagnostic tests is dependent upon understanding the immune responses of the host animal during infection. This paper presents information on populations of immune cells present in different stages of disease. Further work on host immunity will lead to better understanding of the pathogenesis of disease and aid in new preventative and therapeutic regimes.
Technical Abstract: CD5 is a cell surface molecule involved in antigen recognition and is present on all T lymphocytes and a subset of B lymphocytes. The purpose of this study was to examine CD5+ expression on peripheral blood B cells from healthy, noninfected cattle and cattle with subclinical and clinical paratuberculosis. Peripheral blood mononuclear cells (PBMC) were freshly isolated, or cultured for 7 days in the presence or absence of live Mycobacterium avium subsp. paratuberculosis (M. avium subsp. paratuberculosis), and then analyzed by flow cytometry for CD5 expression within the B cell subpopulation. Analysis demonstrated a significant increase (P < 0.01) in B lymphocytes in clinical animals as compared to healthy control cows and subclinically infected cows. In addition, three distinct subpopulations within the CD5+ B cell population were identified: CD5dim, CD5bright, and CD5extra bright. A decrease in the CD5dim B cell population along with a concomitant increase in CD5bright B cells was observed in infected cows, an effect that was highly significant (P < 0.01) for subclinically infected cows in cultured PBMC. In vitro infection with live M. avium subsp. paratuberculosis did not result in significant changes in B cell populations or affect CD5+ expression patterns on B lymphocytes, regardless of animal infection status. Animals were tested for Bovine Leukemia Virus (BLV) as a possible contributor to changes in CD5+ expression with no significant effects noted in this study. These results suggest that differential CD5+ expression on B lymphocytes in animals with paratuberculosis may reflect a shift in host immunity during the disease process.