The Effects of EGCG on Costimulatory Molecule Expression by Legionellalnfected Dendritic Cells

A recent study concerning the effects of Lp infection of DCs showed that EGCG treatment inhibited surface expression of co-stimulatory molecules by BMDCs from Lp-resistant BALB/c mice (Fig. 10.2). Expression of co-stimulatory molecules is a marker of DC maturation and associated with enhanced ability to activate resting T cells. Studies showed that EGCG treatment of cultured Lp-infected DCs inhibited the Lp-induced expression of both MHC class l and class ll molecules important for DC maturation. Mature DCs process exogenous antigens intracellularly and present them to T cells within the context of MHC class ll molecules, although most cells use MHC class l molecules to present peptides derived from endogenously synthesized proteins. However, DCs can deliver exogenous antigens directly to the MHC class l pathway, a phenomenon known as cross-presentation important for resistance of cells infected with Lp (Haycock, 1993; Heath et al., 2004). The inhibitory effects of EGCG on co-stimulatory/MHC molecule expression occurs simultaneously but to a greater extent than EGCG effects on the percentage of cells expressing the CD11c surface marker. lnterestingly, exposure of DCs to Lp increased the percentage of cells expressing the surface marker CD11c, whereas untreated DCs evince the typical decreased CD11 c percentage, down to near control levels. Such results suggest that CD11c is a marker for DC maturation.

OConly DC4Lp OC+l|HEGCG(IHI| DC1Lp»EGCG(30) DCHjHEGCEp«)

OConly DC4Lp OC+l|HEGCG(IHI| DC1Lp»EGCG(30) DCHjHEGCEp«)

Cd11c Marker

CD11C

Figure 10.2. EGCG inhibits Legionella pneumophila (Lp) upregulation of MHC class I/II and co-stimulatory molecule expression by DCs infected with Lp and treated with various concentrations of EGCG and analyzed by FACS. Numbers in quadrants reflect percentages rounded to next greater whole integer. Results shown are 1 of 5 independent experiments with similar results.

CD11C

Figure 10.2. EGCG inhibits Legionella pneumophila (Lp) upregulation of MHC class I/II and co-stimulatory molecule expression by DCs infected with Lp and treated with various concentrations of EGCG and analyzed by FACS. Numbers in quadrants reflect percentages rounded to next greater whole integer. Results shown are 1 of 5 independent experiments with similar results.

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