the invention relates to an aqueous solution containing at least one species selected from the group consisting of a 1 : 1 molar complex of teo 2 with a moiety of formula and ammonium salts thereof : ho — x — oh ; where x is an optionally substituted divalent saturated hydrocarbon group containing 2 - 8 carbon atoms in the chain connecting the two oh groups ; and its use for stimulating cells to produce cytokines and for treating mammalian diseases and conditions responsive to increased production of cytokines . the complex may be used also for treating mammalian cancer which is not responsive to increased production of cytokines .