Immunosuppressive activity of two plant steroidal lactones withaferin A and withanolide E.

Withaferin A and withanolide E, two steroidal lactones of plant origin were demonstrated to have specific immunosuppressive effects on human B and T lymphocytes as well as on mice thymocytes. E rosettes and EAC rosette formation by normal human T and B lymphocytes were inhibited by the two compounds at very low concentrations. The formation of mouse red blood rosettes by chronic lymphatic leukemic cells were only inhibited by withaferin A. The functional activity of normal human T lymphocytes as assessed by a local xenogeneic graft versus host reaction was also affected by these two plant steroidal lactones. These experiments demonstrate a specific action of the compound on antigen recognition as well as proliferative capacity of T lymphocytes as well as B lymphocytes.