|KRUEGER, L - IOWA STATE UNIVERSITY|
|BEITZ, D - IOWA STATE UNIVERSITY|
Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/1/2016
Publication Date: 9/7/2016
Citation: Krueger, L.A., Beitz, D.C., Humphrey, S.B., Stabel, J.R. 2016. Gamma delta T cells are early responders to Mycobacterium avium subsp. paratuberculosis in colostrum-replete Holstein calves. Journal of Dairy Science. 99(11):9040-9050. doi: 10.3168/jds.2016-11144.
Interpretive Summary: Morbidity and mortality in neonatal calves is a major concern for dairy producers. Evidence suggests that calves can become infected shortly after birth by exposure to pathogens such as Mycobacterium avium subsp. paratuberculosis, Salmonella, and Mycoplasma in either the feces or milk of infected dams, bedding or cohabitation with other infected animals. These pathogens may be spread to calves through colostrum or waste milk from sick or infected cows. Some producers have opted to feed colostrum replacers and/or pasteurized whole milk to their calves to avoid the potential spread of disease. However, the vitamin content of milk is negligible and may be impacting the immune response of neonatal calves to infectious pathogens. This study demonstrated that depriving calves of colostrum directly impacted the composition of their immune cells. This information provides a useful management tool for dairy producers in allaying the spread of infectious disease to their calves and improving their health.
Technical Abstract: Peripheral blood mononuclear and mesenteric lymph node cells (PBMC and MNL, respectively) were obtained from 30 calves that were assigned randomly at birth to one of six treatment groups: 1) colostrum deprived (CD), no vitamins; 2) colostrum replacer (CR), no vitamins; 3) CR, vitamin A; 4) CR, vitamin D3; 5) CR, vitamin E; 6) CR, vitamins A, D3, E, with 5 calves per treatment in a 14 d (day) study. Calves were injected with appropriate vitamin supplements and fed pasteurized whole milk (CD calves) or fractionated colostrum replacer (CR) at birth. Thereafter, all calves were fed pasteurized whole milk fortified with vitamins according to treatment. Calves were orally inoculated with 10**8 cfu of Mycobacterium avium subsp. paratuberculosis (MAP) on d 1 and 3 of age. PBMC and MNL were analyzed by flow cytometry as fresh cells, after 3 d culture with PHA, and after 6 d culture with a whole cell sonicate of MAP (MPS). Peripheral gamma delta T cells constitutively expressed CD25 more abundantly than did other PBMC and were identified as a predominant lymphocyte subset, with a decreased percentage noted in CD calves. Stimulation of PBMC with PHA resulted in increased CD4**+ and CD8**+ subsets, whereas the MNL response was dominated by expansion of IgM**+ B cell population. PHA and MPS stimulation decreased the relative abundance of gamma delta T cells among PBMCs, but MNL gamma delta T cells increased upon stimulation with MPS. These results identify gamma delta T cells as key early responders to intracellular infection in neonatal calves and suggest that colostrum may be an important mediator of this response.