Based on polymerase chain reaction (PCR) utilizing degenerate primers directed to the second and sixth transmembrane domains of several G-protein-coupled neurotransmitter receptors and screening of a human B-lymphoblast cDNA library, we isolated a cDNA whose predicted amino acid sequence shows considerable homology with human chemoattractant receptors, e.g., 30% overall identity with the C5a anaphylatoxin receptors. The coding region consists of 1056 bp corresponding to 352 amino acid residues and giving an approximate molecular weight of 43 kDa. Northern blot analysis showed hybridizing transcripts in spleen, thymus, and lymph nodes, as well as in bone marrow and peripheral blood leukocytes. Message was also found in lymphoid tumor cell lines. Chromosome mapping with FISH/DAPI technique showed the corresponding gene to reside on human chromosome 14q11.2-q12. In accordance with the Genome Database Nomenclature the receptor was designated CMKRL1 ("chemoattractant receptor-like 1"). Stably transfected mammalian cells (CHO cells and LVIP2.0Zc reporter cells) expressing high levels of corresponding receptor RNA were analyzed for changes in cAMP concentration and cellular calcium fluxes. Chemokines tested to date (GRO-a, MCP-1, MCP-3, MIP-1a, MIP-1b, C5a, RANTES, and LTB4) have failed to elicit any reproducible response. Although the ligand for CMKRL1 could thus not be identified among chemotactic peptides, the high expression in lymphoid cells and tissues suggests that the receptor may function in the regulation of the inflammatory system.