Brazilein, an important immunosuppressive component from Caesalpinia sappan L.

Caesalpinia sappan has been shown to have interesting immunosuppressive properties. Its heartwood has long been used in Chinese medicines for treating a variety of immune-mediated pathology and inflammatory disease. The purpose of this work was to evaluate the immunocompetence effects of brazilein on mice lymphocytes in vitro and in vivo. The results showed that brazilein and Caesalpinia sappan ethanol extract (SME) could distinctly inhibit the proliferation of T lymphocyte stimulated by Concanavalin A (Con A) and the proliferation of B lymphocyte stimulated by lipopolysaccharides (LPS), and brazilein could suppress mice humoral immune response by plaque forming cell (PFC) test. In addition, immune organs (thymus and spleen) in mice treated with brazilein were notably atrophied and weight loss in vivo (intraperitoneal injection, i.p.). In attempting to investigate the mechanisms of the immunosuppressive activity of brazilein, we discovered that brazilein can induce apoptosis in mice spleen lymphocytes by flow cytometry analysis and DNA fragmentation assay, which may be one of the pathways that brazilein inhibited immunocompetence of mice lymphocytes.