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By searching the expressed sequence tag (EST) data base, we identified partial cDNA sequences encoding a novel human CC chemokine. We determined the complete cDNA sequence that encodes a highly basic polypeptide of a total 98 amino acids with 20 to 30% identity to other human CC chemokines. We termed this novel chemokine from EBI1-Ligand Chemokine as ELC (see below). The ELC mRNA was most strongly expressed in the thymus and lymph nodes. Recombinant ELC protein was expressed as a fusion protein with the Flag tag (ELC-Flag). For receptor-binding assays, recombinant ELC protein fused with the secreted form of alkaline phosphatase (SEAP) was used. By stably expressing five CC chemokine receptors (CCR1 to 5) and five orphan receptors, ELC-SEAP was found to bind specifically to an orphan receptor EBI1. Only ELC-Flag, but not MCP-1, MCP-2, MCP-3, eotaxin, MIP-1alpha, MIP-1beta, RANTES (regulated on activation normal T cell expressed and secreted), thymus and activation-regulated chemokine (TARC), or liver and activation-regulated chemokine (LARC), competed with ELC-SEAP for EBI1. ELC-Flag-induced transient calcium mobilization and chemotactic responses in EBI1-transfected cells. ELC-Flag also induced chemotaxis in HUT78 cells expressing endogenous EBI1 at high levels. By somatic hybrid and radiation hybrid analyses, the gene for ELC (SCYA19) was mapped to chromosome 9p13 instead of chromosome 17q11.2 where the genes for CC chemokines are clustered. Taken together, ELC is a highly specific ligand for EBI1, which is known to be expressed in activated B and T lymphocytes and strongly up-regulated in B cells infected with Epstein-Barr virus and T cells infected with herpesvirus 6 or 7. ELC and EBI1 may thus play roles in migration and homing of normal lymphocytes, as well as in pathophysiology of lymphocytes infected with these herpesviruses. We propose EBI1 to be designated as CCR7.

Partial overlapping cDNA sequences likely to encode a novel human CC chemokine were identified from the GenBank Expressed Sequence Tag data base. Using these sequences, we isolated full-length cDNA encoding a protein of 96 amino acid residues with 20-28% identity to other CC chemokines. By Northern blot, this chemokine was mainly expressed in liver among various tissues and strongly induced in several human cell lines by phorbol myristate acetate. We thus designated this chemokine as LARC from Liver and Activation-Regulated Chemokine. We mapped the LARC gene close to the chromosomal marker D2S159 at chromosome 2q33-q37 by somatic cell and radiation hybrid mappings and isolated two yeast artificial chromosome clones containing the LARC gene from this region. To prepare LARC, we subcloned the cDNA into a baculovirus vector and expressed it in insect cells. The secreted protein started at Ala-27 and was significantly chemotactic for lymphocytes. At a concentration of 1 microg/ml, it also showed a weak chemotactic activity for granulocytes. Unlike other CC chemokines, however, LARC was not chemotactic for monocytic THP-1 cells or blood monocytes. LARC tagged with secreted alkaline phosphatase-(His)6 bound specifically to lymphocytes, the binding being competed only by LARC and not by other CC or CXC chemokines. Scatchard analysis revealed a single class of receptors for LARC on lymphocytes with a Kd of 0.4 nM and 2100 sites/cell. Collectively, LARC is a novel CC chemokine, which may represent a new group of CC chemokines localized on chromosome 2.