|Kehrli Jr, Marcus|
Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/23/2003
Publication Date: 7/20/2003
Citation: Nonnecke, B.J., Kimura, K., Goff, J.P., Kehrli Jr, M.E. 2003. Effects of the mammary gland on functional capacities of blood monoculear leukocyte populations from periparturient cows. Journal of Dairy Science. 86(7):2359-2368. Interpretive Summary: During the days immediately before and after calving (i.e. the periparturient period), the dairy cow experiences a state of immunosuppression that is associated with a heightened susceptibility to infectious diseases. Frequently, these infections are associated with increased morbidity and mortality, and reduced production resulting in significant economic losses to the producer. Factors contributing to the apparent reduction in immune competency during this period are likely diverse and interdependent. The most influential of these likely includes those associated with the metabolic demands of pregnancy and lactation. Objectives of this study were to evaluate the function of immune cells from periparturient cows and, secondly, determine if changes in function could be, at least in part, attributable to the metabolic demands of lactation. To achieve this goal, functions of blood-borne immune cells from intact and mastectomized (i.e. mammary surgically removed) cows were evaluated at regular intervals beginning 21 days before calving and concluding at 19 days after calving. Results indicated that several cell functions that play a critical role in the development of an effective immune response were more compromised in intact cows than in mastectomized cows. These results suggest that lactation-specific alterations in metabolism influence negatively immune cell function in the recently calved dairy cow. These results also suggest a new direction for studies evaluating mechanisms for optimizing immune function in the periparturient dairy cow. The results of this research will have significant impact on the dairy industry worldwide.
Technical Abstract: The composition and functional capacity of peripheral blood mononuclear leukocyte populations from dairy cows are altered substantially during the peripartal period. These changes are associated with a heightened susceptibility of the mammary gland to infection. It has been postulated that the metabolic demands associated with lactogenesis may impact negatively leukocyte function during the periparturient period. In the present study, serum immunoglobulin G1 concentration and functional capacities of peripheral blood mononuclear leukocytes from intact (n=6) and mastectomized (n=6) periparturient Jersey cows were evaluated and compared. Cell functions included DNA synthesis, immunoglobulin M secretion, and interferon-gamma secretion by unstimulated and pokeweed mitogen stimulated mononuclear leukocytes. Data were summarized as mean responses for 5-day periods beginning 21days prepartum and concluding at 19 days postpartum. The progressive decrease in serum immunoglobulin G1 in intact but not mastectomized cows before parturition likely was attributable to the selective uptake of this isotype by the mammary gland. Synthesis of DNA and secretion of interferon-gamma and polyclonal IgM by mitogen-stimulated leukocytes from intact cows decreased during the 15 day period before calving, reaching a nadir at 0 to 4 days postpartum. From 5 to 19 days postpartum, these functions often were comparable to those observed two to three weeks prepartum. Functions of leukocytes from mastectomized cows did not change during the study period, although they often were of lower magnitude than those of cells from nonlactating cows. These results reconfirm the occurrence of a generalized reduction in blood mononuclear leukocyte function during the periparturient period. They also suggest that the reduction in leukocyte function during the period may be, in part, due to the physiologic demands imposed on the dairy cow by the lactating mammary gland.