Advanced Targeting Systems has introduced important new toxins for investigation into cells that express the interleukin-2 (IL-2) receptor and especially the workings of the immune system. Anti-CD25-saporin (Anti-Tac-SAP) conjugates are directed to the human IL-2 receptor or to the mouse IL-2 receptor. This marker for activated T lymphocytes allows removal of this important group of cells and determination of their function in numerous important biological responses. The graph below shows the potent cytotoxic activity of the anti-human CD25-saporin toxin (anti-Tac-SAP, Cat. #IT-24).