Immunomodulation of Isolated Human Neutrophils by a Green Tea Extract

ABSTRACT Over the last few years certain phytochemicals have been advocated as immunomodulatory agents. We have screened three commercially available extracts of ginger, echinacea, and green tea to investigate if they can prime isolated human neutrophils. The efficacy of these phytochemicals was compared to a recognised neutrophil priming agent GM-CSF. In this study, priming was defined as the ability of the neutro-phils to release more superoxide and myeloperoxidase when challenged with the bacterial peptide fMet-Leu-Phe. The green tea extract was shown to prime neutrophils, with optimal activity following a 30 min incubation at 37°C, after washing the cells and then stimulating with fMet-Leu-Phe. The green tea treated neutrophils produced more superoxide (11.4 ± 0.71 nmoles/106 vs. control cells 5.7 ± 0.8 nmoles/106 neu-trophils) and released more myeloperoxidase (3.9% ± 0.1 vs. control cells 0.7% ± 0.7) than the control cells. Priming of human neutrophils with GM-CSF induced tyrosine kinase activity, that resulted in a distinct phosphorylation pattern. The priming mechanism of green tea was not similar to that of GM-CSF as no tyrosine kinase activity was observed in the cells during the priming process. The reported neutrophil priming effects of the green tea extract are novel and may promote further health benefits in immunocompromised patients.

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