Cutting Edge: Identification of GL50, a Novel B7-Like Protein That Functionally Binds to ICOS Receptor

• Published in: The Journal of immunology (1950) 2000-02, Vol.164 (4), p.1653-1657
• Main Authors: Ling, Vincent, Wu, Paul W, Finnerty, Heather F, Bean, Kevin M, Spaulding, Vicki, Fouser, Lynette A, Leonard, John P, Hunter, Sharon E, Zollner, Richard, Thomas, Jenifer L, Miyashiro, Joy S, Jacobs, Kenneth A, Collins, Mary
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Animals; Antigens, CD - chemistry; Antigens, CD - genetics; Antigens, CD - isolation & purification; Antigens, CD - metabolism; Antigens, Differentiation, T-Lymphocyte - metabolism; B7-1 Antigen - chemistry; B7-1 Antigen - genetics; B7-1 Antigen - isolation & purification; B7-1 Antigen - metabolism; B7-2 Antigen; Blotting, Northern; Cloning, Molecular; DNA, Complementary - isolation & purification; Humans; Inducible T-Cell Co-Stimulator Ligand; Inducible T-Cell Co-Stimulator Protein; Ligands; Lymph Nodes - chemistry; Lymph Nodes - metabolism; Membrane Glycoproteins - chemistry; Membrane Glycoproteins - genetics; Membrane Glycoproteins - isolation & purification; Membrane Glycoproteins - metabolism; Mice; Mice, Inbred BALB C; Mice, Inbred C57BL; Molecular Sequence Data; Proteins - chemistry; Sequence Alignment; Transcription, Genetic - immunology; Tumor Cells, Cultured
• ISSN: 0022-1767; 1550-6606
• DOI: 10.4049/jimmunol.164.4.1653

By the genetic selection of mouse cDNAs encoding secreted proteins, a B7-like cDNA clone termed mouse GL50 (mGL50) was isolated encoding a 322-aa polypeptide identical with B7h. Isolation of the human ortholog of this cDNA (hGL50) revealed a coding sequence of 309 aa residues with 42% sequence identity with mGL50. Northern analysis indicated GL50 to be present in many tissues including lymphoid, embryonic yolk sac, and fetal liver samples. Of the CD28, CTLA4, and ICOS fusion constructs tested, flow cytometric analysis demonstrated only mouse ICOS-IgG binding to mGL50 cell transfectants. Subsequent phenotyping demonstrated high levels of ICOS ligand staining on splenic CD19+ B cells and low levels on CD3+ T cells. These results indicate that GL50 is a specific ligand for the ICOS receptor and suggest that the GL50-ICOS interaction functions in lymphocyte costimulation.