Anthraquinones of edible wild vegetable Cassia tora stimulate proliferation of human CD4+ T lymphocytes and secretion of interferon-gamma or interleukin 10

Cassia tora L. is an edible wild plant. This study evaluated the immunostimulatory activities of four anthraquinones of C. tora (aloe-emodin, emodin, chrysophanol, and rhein) on human peripheral blood mononuclear cells (PBMC). Studies were conducted on lymphocyte proliferation by BrdU immunoassay, secretion of interferon-gamma (IFN-γ) and interleukin 10 (IL-10) by an ELISA assay and elucidation of responding immune cells by flow cytometry. The results showed that at non-cytotoxic concentrations, the tested anthraquinones were effective in stimulating the proliferation of resting human PBMC and/or secretion of IFN-γ. However, at the concentration of 10 μg/ml (35 μM), rhein significantly stimulated proliferation of resting human PBMC (stimulation index (SI) = 1.53), but inhibited IFN-γ secretion (74.5% of control). The augmentation of lymphocyte proliferation was correlated to the increase in number of CD4+ T cells, while the elevated secretion of IFN-γ and IL-10 might have been due to the activated CD4+ T cells.