Plasma γ-globulin fraction proteins, copper cations, and metal complexes formed by copper cations with human serum γ-globulin induce the production of up to 4.0 ng/ml IL-8 by human blood cells. Protein modified by copper cations is 1.3-1.7-fold (p < 0.001-0.01) more potent than control γ-globulin and 1.3-fold (p < 0.001) more potent than copper cations alone. Analysis of the time course of IL-8 production demonstrated that IL-8 is produced as a prolonged or delayed response cytokine under conditions of this induction.