Abstract: Immunoreactive cells sensitized for an antigenic marker associated with a malignant tumor are prepared in vitro by collecting the tumor patient's own mononuclear cells, depleting suppressor T-cells, suspending the mononuclear cells with serum, preferably autologous, and culturing the cells under conditions to activate and immunize the patient's mononuclear cells against the patient's tumor. Methods of treatment and immunized cells in pharmaceutical presentations are described.