In vitro immunomodulatory effects of cuphiin D₁ on human mononuclear cells

Cuphiin D₁ (CD₁), a macrocyclic hydrolyzable tannin isolated from Cuphea hyssopifolia, has been shown to exert antitumor activity both in vitro and in vivo. Moreover, the antitumor effects of CD₁ are not only related to its cytotoxicity to carcinoma cell lines, but also depend on host-mediated mechanisms. In the present study, CD₁ was investigated for its effects on the proliferation and cytokine secretion of human peripheral blood mononuclear cells (PBMCs). At concentrations of from 6.25 to 50 μg/ml, it enhanced the ³H-thymidine incorporation of concanavalin A (Con A)-stimulated PBMCs in a dose-dependent manner. Excretion of IL-1β, IL-2 and TNF-α by CD₁-stimulated PBMCs was markedly increased in a dose-dependent manner. The results show that CD₁ could stimulate PBMCs release of IL-1β, IL-2 and TNF-α and then activate T cells. Therefore, CD₁-activated T cells via IL-1β in vitro might account for the host-mediated CD₁ mechanism of action.