In this instance, BsAbs constructed with murine antibodies containing one Fab arm against either CD19 or CD22 and the other against saporin were investigated in just two patients with either end stage B-cell chronic lymphocytic leukaemia (CLL) or B-cell follicle centre centrocytic/centroblastic lymphoma. The gene discussed is CD22; the disease is B-cell chronic lymphocytic leukemia.