IL-8 induces chemotaxis of human neutrophils and lymphocytes but does not stimulate eosinophils. The chemotactic activity was measured using the modified Boyden chamber technique and expressed as the CI, defined as the ratio of the number of migrating cells in presence of stimulus versus migrating cells in the presence of medium. Cells were incubated with the indicated stimuli. The results are presented as the mean ± SEM of five different experiments. (□) Eosinophils; () neutrophils; (▩) lymphocytes.