In this study we present the cloning, characterization and expression analysis of a cDNA encoding a rat interleukin-8 receptor (rIL-8R). A 1324 bp cDNA containing an open reading of 359 amino acids with an 86.1% overall identity with the previously characterized mouse IL-8R was isolated. Genomic DNA analysis using several restriction enzymes revealed a single band suggesting that the rIL-8R gene exists as a single-copy, which is in contrast to humans where there are two different IL-8Rs genes. Expression of rIL-8R mRNA was found in several tissues including spleen, heart, lung, liver, skeletal muscle and kidney. In brain and testis rIL-8R mRNA was not detectable. Rat IL-8R mRNA expression at the cellular level was studied in the spleen using RNA-RNA in situ hybridization and immunohistochemistry. IL-8R mRNA containing cells were predominately found in the mantle zone of the germinal center. These cells were identified as B lymphocytes using the OX-33 monoclonal antibody.