Neutrophil leukocytes, the target cells for interleukin-8 and related CXC chemokines, bear high numbers of two types of IL-8 receptors (IL-8Rl and IL-8R2). By cDNA transfection Jurkat cell lines were generated that stably express either IL-8Rl or IL-8R2 (J-IL8Rl and J-IL8R2). J-IL8Rl expressed 4,000 + 1,000 copies of IL-8R1, and bound IL-8 with high affinity (Kd l-4 nM) and GROcl and NAP-2 with low affinity (Kd 200-500 nM). J-IL8R2 expressed 17,000 f 3,000 copies of IL-8R2, and bound all three chemokines with high affinity. Both transfectants showed a similar degree of chemotactic migration after stimulation with IL-8, GROa and NAP-2. All three chemokines were equally potent as attractants of J-IL8R2, whereas IL-8 was 300 to l,OOO-fold more potent than GROcl or NAP-2 as attractant of J-IL8Rl. The potencies, therefore, agree with the affinities of the ligands to IL-8Rl and IL-8R2. Our results demonstrate that both IL-8 receptors function independently, and mediate chemotaxis in response to IL-8 and other CXC chemokines.