Regulation of murine dendritic cell functions in vitro by taurine chloramine, a major product of the neutrophil myeloperoxidase-halide system

Abstract

Taurine chloramine (TauCl) is a major chloramine generated in activated neutrophils as a result of the reaction of highly toxic hypochlorous acid and taurine, the most abundant free amino acid in cytosol. In this study we have tested the influence of TauCl on the properties of murine dendritic cells (DC), the major cell population involved in the initiation of an adaptive immune response against pathogenic organisms. N418+, MHC II+, B7-2+ dendritic cells, generated from the mouse bone marrow cells cultured in the presence of granulocyte-macrophage colony-stimulating factor, were stimulated by interferon-gamma and lipopolysaccharide to produce nitric oxide, reactive oxygen species, interleukin-6 (IL-6), tumour necrosis factor-alpha, and IL-12, in the presence of different doses of TauCl. TauCl differently inhibited the generation of these inflammatory mediators in a dose-dependent manner. Furthermore, TauCl selectively modulated the ability of DC to induce the release IL-2 and IL-10 from T cells. These results suggest that neutrophil-derived mediators, such as TauCl, at a site of inflammation, may affect the functions of sentinel DC and macrophages, and play a role in maintaining the balance between the inflammatory response and the induction of an antigen-specific immune response.

Figure 1

The effect of TauCl on production of inflammatory mediators by DC. (a) DC (5 × 10⁵/well/ml) were preincubated with TauCl for 2 hr and than the cells were cultured in the presence of LPS (100 ng/ml) and IFN‐γ (20 U/ml). After 24 hr, supernatants were collected and TNF‐α, IL‐6, IL‐10 and IL‐12 were measured by ELISA. (b) DC were cultured as above, and nitrite release was measured by Griess reaction. (c) DC were cultured as above, and PGE₂ was measured by ELISA. Results are expressed as the average percentage (± SD) compared to the control group (stimulated DC without TauCl), and are calculated from six independent experiments; * P < 0·05.

Figure 2

The effect of TauCl on luminol‐dependent chemiluminescence (LCL) from DC stimulated with opsonized zymosan. DC (5 × 10⁵/well) were dark adapted in the presence of either luminol alone or luminol and TauCl (0·1–0·5 mm) for 60 min. Chemiluminescence reaction was recorded immediately after the stimulation with zymosan over 3600 seconds. The total area under the curves is shown in the key to the figure. The figure shows the results of one of five separate experiments.