Flavone acetic acid (FAA) enhances natural killer and lymphokineactivated killer (LAK) cell activity in mice. We examined the immunological effects of FAA on human blood cells both in vivo and in vitro. Peripheral blood natural killer and LAK activity and lymphocyte subsets were evaluated in cancer patients after receiving 3-h infusion of FAA at either 8.5 or 10 g/m2 with alkalinization. Natural killer cell activity and the number of Leu-19 (CD56) positive cells decreased at 24 h after infusion; significant changes in LAK activity and the number of Leu-1 (CD5), Leu-3 (CD4), Leu-2 (CD8) cells were not observed. Peripheral blood mononuclear cells and peripheral blood lymphocytes collected from healthy volunteers were exposed in vitro to FAA, interleukin 2, and FAA plus interleukin 2. FAA, alone or in combination, failed to enhance LAK activity at any time point or concentration from peripheral blood mononuclear cells and peripheral blood lymphocytes. Concentrations of ≥100 µg/ml antagonized the generation of LAK activity from interleukin 2 treated peripheral blood lymphocytes. These data suggest that FAA may not be useful in enhancing immunological responses in humans.

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