The primary polyphenol in green tea extract is the catechin epigallocatechin gallate (EGCG). Various studies have shown significant suppressive effects of catechin on mammalian cells, either tumor or normal cells, including lymphoid cells. Previous studies from this laboratory reported that EGCG has marked suppressive activity on murine macrophages infected with the intracellular bacterium Legionella pneumophila (Lp), an effect mediated by enhanced production of both tumor necrosis factor-alpha (TNF-alpha) and gamma-interferon (IFN-gamma). In the present study, primary murine bone marrow (BM)-derived dendritic cells (DCs), a phagocytic monocytic cell essential for innate immunity to intracellular microorganisms, such as Lp, were stimulated in vitro with the microbial stimulant lipopolysaccharide (LPS) from gram-negative bacteria, the cell wall component from gram-positive bacteria muramyldipeptide (MDP) or infected with Lp. Production of the T helper cell (Th1)-activating cytokine, interleukin-12 (IL-12) and the proinflammatory cytokine, tumor necrosis factor-alpha (TNF-alpha),produced mainly by phagocytic cells and important for antimicrobial immunity, was determined in cell culture supernatants by enzyme-linked immunosorbent assay (ELISA). Treatment of the cells with EGCG inhibited, in a dose-dependent manner, production of IL-12. In contrast, enhanced production of TNF-alpha occurred in a dose-dependent manner in the DC cultures stimulated with either soluble bacterial product or infected with Lp. Thus, the results of this study show that the EGCG catechin has a marked effect in modulating production of these immunoregulatory cytokines in stimulated DCs, which are important for antimicrobial immunity, especially innate immunity. Further studies are necessary to characterize the physiologic function of the effect of EGCG on TNF-alpha and IL-12 during Lp infection, and the mechanisms involved.

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An enzyme-linked immunosorbent assay for Treponema pallidum antibody (Syphilis Bio-EnzaBead Kit; Organon Teknika Corp., formerly Litton Bionetics, Kensington, Md.) was compared with the standard fluorescent treponemal antibody absorption test for syphilis (indirect fluorescent-antibody confirmatory test; Zeus Scientific Inc., Raritan, N.J.). Six hundred specimens tested in the rapid plasma Reagin card test (Hynson, Westcott and Dunning, Inc., Baltimore, Md.) and microhemagglutination assay for antibodies to T. pallidum (Ames Division, Miles Laboratories, Inc., Elkhart, Ind.) were used for comparison testing. One hundred and sixty-two specimens were from either persons with syphilis or persons whose history was unknown but who showed reactive serology, whereas 438 were from persons without syphilis. The reactivity of each serum by the Bio-EnzaBead test was determined visually and from optical density readings. Excellent reproducibility of visual readings was obtained; all results were within ± 1 gradation of the expected readings in all 60 coded sera tested. Overall agreement between the Bio-EnzaBead and fluorescent treponemal antibody absorption test results was 96.3% when read visually and .95.7% when using optical density readings. Our data indicate that Bio-EnzaBead results read at 405 nm and determined by using the mean antigen optical density reading of the nonreactive control plus 0.025 as the cutoff value provide an overall sensitivity and specificity of 93.0 and 98.6%, respectively, along with the best agreement with the fluorescent treponemal antibody absorption assay. Ease of performance and objectivity also contribute toward the acceptability of this assay as an alternative confirmatory test for syphilis.

Dendritic cells (DCs) have a critical role in linking innate to adaptive immunity, and this transition is regulated by the up-regulation of costimulatory and major histocompatibility complex (MHC) molecules as well as Toll-like receptors. These changes in DCs have been observed to occur following microbial infection, and in the present study, we examined the effect of Legionella pneumophila infection on the expression of these DC markers. We showed that bone marrow-derived DC cultures from BALB/c mice infected with live L. pneumophila resulted in the up-regulation of Toll-like receptors 2 and 4 and the activation of CD40, CD86, and MHC class I/II molecules.