Bovine Macrophage Cell Research Articles

Temporal effects of tumor necrosis factor-α on intracellular survival of Mycobacterium paratuberculosis

The causative agent in Johne's disease is Mycobacterium paratuberculosis, an intracellular pathogen which causes enteritis in ruminants. Little is known about interactions between the host cell (macrophage) and M. paratuberculosis; however, this bacterium is able to evade normal host immune defenses and cause a chronic infective state. In the present study, we evaluated whether activation of a murine macrophage cell line (J774.16) by pretreatment with recombinant murine tumor necrosis factor alpha (TNF) prior to infection with M. paratuberculosis would affect their ability to restrict growth and kill the ingested bacteria. A murine cell line was utilized owing to difficulty in obtaining bovine reagents and lack of a continuous bovine macrophage cell line for repeated experimentation. After 4 h of infection, numbers of viable bacteria in cell lysates were significantly lower for macrophages pretreated with 1000 IU TNF ml −1. The rate of bacterial growth as assessed by BACTEC radiometric culture system was also reduced at this time point. Upon further extension of the infection period to 72 h, we observed that moderate doses of TNF (10–1000 IU ml −1) significantly increased the number of viable M. paratuberculosis recovered whereas the highest dose of TNF (4000 IU ml −1) effectively reduced bacterial numbers. These data indicate that TNF can either enhance or reduce macrophage mycobactericidal and mycobacteriostatic activity depending upon both the level of TNF to which cells are exposed and the duration of infection.

Establishment of a bovine macrophage cell line from a fetal thymus.

A cell line, FBM-17, was established from a fetal bovine thymus and passaged for more than a year. Electron microscopic examination revealed that the cytoplasm contained many phagosomes and a significant amount of rough endoplasmic reticula. In addition, FBM-17 cells showed non-specific esterase, phagocytosis and surface expression of Fc receptors for IgG and classes I and II MHC antigens. These observations confirmed that this cell line had the morphologic and functional features as a macrophage. MHC expression markedly increased by treatment with recombinant bovine gamma-interferon, showing the cell line to be sensitive to bovine gamma-interferon and functional. These present results suggest that the FBM-17 is a functional bovine macrophage cell line. This line gamma-interferon, showing the cell line to be useful for clarification of roles of macrophages in immunoregulation in cattle.

In vitro Activation of Bovine Macrophage and Peripheral Blood Mononuclear Cells by Nocardia rubra Cell Wall Skeleton (N‐CWS)

Nocardia rubra cell wall skeleton (N-CWS) was used for immunotherapy to bovine leukemia virus (BLV)-positive cattle with enlarged subcutaneous lymphatic nodules. Electron microscopical observations showed the infiltration of macrophage and T cells around N-CWS treated lesions. Antitumor effect induced by N-CWS was examined in vitro. The maximum cytolytic activity of macrophage was observed, when the cells were incubated with 10 micrograms/ml of N-CWS. Chemiluminescence response of peripheral blood mononuclear cells (PBMC) using N-CWS as stimulant was observed with a high level of activity for a long period, 5 hr. Mitogenic effect of N-CWS to PBMC was observed in the presence of macrophages but not without macrophages. Furthermore, interleukin 2 activity was recognized in supernatant of PBMC cultured with N-CWS. Maximum cytotoxic T lymphocyte response was induced when PBMC were cultured with 0.1 micrograms/ml of N-CWS.