Anticytokine antibodies in individual IgG preparations and increased serum cytokine binding capacities after therapy. For each cytokine, the antibody capacities were expressed relative to an arbitrary standard activity of one of the IgG batches. All activities were therefore expressed as mg equivalents/mL serum or mg equivalents/mg IgG of the respective standards. The correlation values were: r: 0.83, P < .001 (IFNα2A), r: 0.77, P < .001 (IL-1α), and r: 0.623, P < .001 (IL-6).