Modulation ofMycobacterium bovis-Specific Responses of Bovine Peripheral Blood Mononuclear Cells by 1,25-Dihydroxyvitamin D₃

Abstract

(48) and Zairians living in Belgium (35) compared to control individuals with less pigmented skin, presumably due to diminished synthesis. Tuberculosis, likewise, is common among individuals with heavily pigmented skin that relocate from equatorial regions to higher latitudes, in part due to deficiencies in vitamin D synthesis within the skin (65). In addition, patients with untreated tuberculosis often have lower concentrations of 25(OH)D 3 in plasma than do healthy subjects, and tuberculosis tends to occur during the winter when exposure to sunlight is reduced and production of cholecalciferol within the skin is diminished (16). Evidence for a clear correlation between vitamin D deficiency and susceptibility to tuberculosis, however, remains controversial. In vitro studies, however, provide more compelling evidence linking vitamin D status to susceptibility to tuberculosis.Addition of 1,25(OH) 2 D 3 to monocyte-macrophage cultures infected with Mycobacterium tuberculosis suppresses bacterial growth and viability (17,53,54). The mechanism of this suppression is mediated, at least partially, by nitric oxide (NO) (53). Induction of inducible NO synthase of macrophages and subsequent generation of reactive nitrogen intermediates (RNI) toxic to mycobacteria is a potent mechanism of killing (14,15,21,22,34). Cytokines (e.g., tumor necrosis factor alpha and gamma interferon [IFN-␥]) from antigen-specific T cells and/or from macrophages stimulated directly with mycobacterial antigens is responsible for RNI-mediated antimycobacterial defense (24,60). Production of RNI is crucial for controlling acute as well as latent infections in the mouse model of virulent M. tuberculosis infection (14,15,25,34). The role of RNI in mycobacterial killing within human macrophages is less clear. Alveolar macrophages of tuberculosis patients express high levels of inducible NO synthase, suggesting a role for RNI in disease pathogenesis and/or host defense (42). Nevertheless, recent evidence suggests that human but not mouse macro-* Corresponding author. Mailing address: United States Department

Expression ofl-Selectin (CD62L), CD44, and CD25 on Activated Bovine T Cells

“…Lesions were most prominent in the lungs and lung-associated lymph nodes (i.e., mediastinal and tracheobronchial). As previously demonstrated (57,58), recall proliferation of PBMC from M. bovisinfected cattle in response to M. bovis PPD was primarily the result of proliferation by CD4 ϩ and ␥␦ TCR ϩ cells (Table 2). Differences in proliferative responses between challenge doses (i.e., 10 3 versus 10 5 CFU) were not detected; thus, data are presented as pooled analyses.…”

“…Peripheral blood mononuclear cells (PBMC) were isolated from buffy coat fractions of blood collected in 2ϫ acid-citrate-dextrose (9). Staining of PBMC with PKH67 was performed according to the manufacturer's instructions (Sigma) and as described elsewhere (56)(57)(58). Briefly, 2 ϫ 10 7 PBMC were centrifuged (10 min, 400 ϫ g), supernatants were aspirated, and cells were resuspended in 1 ml of the diluent provided in the PKH67 kit.…”

1,25-Dihydroxyvitamin D 3 and Development of Tuberculosis in Cattle

“…The suppression of antigen-specific and mitogenic bovine T-cell responses by 1,25-D 3 has previously been described (3), and a more recent study indicated that this inhibitory activity of 1,25-D3 was also to be found in cattle infected with M. bovis (48). We attempted to clarify this effect of 1,25-D 3 in our M. bovis-infected cattle by using a monoclonal antibody raised against the VDR as a receptor agonist.…”

Early Induction of Humoral and Cellular Immune Responses during ExperimentalMycobacterium aviumsubsp.paratuberculosisInfection of Calves

“…Absorbances of standards, controls, and test samples were converted to nanograms per milliliter of nitrite by comparison with absorbances of sodium nitrite (Fisher Chemicals, Fair Lawn, N.J.) standards within a linear curve fit. In prior studies (54), N G -monomethyl-L-arginine (1.15 mM; equimolar to the amount of L-arginine in the culture medium; Calbiochem, La Jolla, Calif.), a competitive inhibitor of the enzyme nitric oxide synthase (NOS), was added to parallel cultures to verify that the nitrite produced was due to the activity of NOS.…”