Swiss Webster mice treated with bolus injections of 'poly-plat' (10 mg/kg) show increased macrophage activation after 2 and 12 days when isolated in cultures. Such macrophages demonstrate an increase in the number of lysosomes and cytoplasmic extension formation with enhanced cytokine (interleukin-1alpha) activity. In addition, peripheral blood smears demonstrated an increase in lymphocytes and monocytes compared to cisplatin-treated animals. These results show that 'poly-plat' activates the immune system more effectively than cisplatin both in vitro and in vivo.