Mast cell migratory response to interleukin-8 is mediated through interaction with chemokine receptor CXCR2/interleukin-8RB

To explore the role of chemokines in mast cell chemotaxis and accumulation at sites of inflammation, we first investigated the response of human mast cells to 18 different chemokines by induction of intracellular calcium mobi lization in the human mast cell line, HMC-1. Only a subgroup of CXC chemoki nes defined by the conserved sequence motif glutamic acid-leucine-arginine (ELR) tripeptide motif, which included interleukin-8 (IL-8), growth-regulat ed oncogene alpha (GRO alpha), neutrophil-activating peptide-2 (NAP-2), and epithelial cell-derived neutrophil activating peptide-78 (ENA-78), induced calcium flux in the cells. These observations suggested that the receptor CXCR2 (IL-8RB) should be expressed on the surface of these cells. Using the RNAse protection assay, CXCR2 mRNA, but not CXCR1 (IL-8RA) mRNA expression was detected in HMC-1 cells. Flow cytometry analysis documented the surfac e expression of CXCR2. A binding analysis performed with I-125-IL-8 determi ned that there were approximately 3,600 high affinity IL-8 binding sites pe r HMC-1 cell, with a calculated kd of 1.2 to 2 nmol/L. The activity of this receptor was further explored using IL-8, which was found to induce dose-d ependent chemotactic and haptotactic responses in both HMC-1 cells and in v itro cultured human cord blood-derived mast cells. These results show the e xpression of functional CXCR2 receptors on the surface of human mast cells, which may play an important role in mast cell recruitment during the genes is of an inflammatory response. (C) 1999 by The American Society of Hematol ogy.