cDNA cloning revealed the presence of two related but distinct types of human interleukin-8 (IL-8) receptors, type I (type A) and type II (type B). By immunizing rabbits with glutathione-S-transferase fused with the NH2-terminal domain of each type of IL-8 receptor, we prepared polyclonal antibodies that specifically recognized the NH2-terminal domain of each type of IL-8 receptor. Immunofluorescence analysis of human peripheral blood leukocytes demonstrated that mature granulocytes except eosinophils express both types of IL-8 receptors. A majority of monocytes and CD16+ natural killer (NK) cells in peripheral blood were stained with both antibodies, whereas CD3+ T or CD20+ B lymphocytes in peripheral blood or CD34+ cells in cord blood were not stained with either antibody. These results suggest that both types of human IL-8 receptors were coordinately and selectively expressed in mature granulocytes, monocytes, and CD16+ NK cells.