Journal of Immunology 164 (9): 4689-4696 (2000-05-01)

Aicher A.; Hayden-Ledbetter M.; Brady W.A.; Pezzutto A.; Richter G.; Magaletti D.; Buckwalter S.; Ledbetter J.A.; Clark E.A.

Characterization of human inducible costimulator ligand expression and function

The inducible costimulator (ICOS) is the newest member of the CD28/CD152 receptor family involved in regulating T cell activation. We constructed a soluble-Ig fusion protein of the extracellular domain of human ICOS and used it as a probe to characterize expression patterns of the ICOS ligand (ICOSL). ICOSIg did not bind to CD80- or CD86-transfected Chinese hamster ovary cell lines, demonstrating that ICOSL is distinct from those ligands identified for CD28/CD152. ICOSIg showed selective binding to monocytic and B cell lines, whereas binding was undetectable on unstimulated monocytes and peripheral blood T and B cells. Expression of ICOSL was induced on monocytes after integrin-dependent plastic adhesion. Pretreatment of monocytes with mAb to the {beta}2-integrin subunit CD18 decreased adhesion and abolished ICOSL up-regulation but had no effect on CD80/86 (CD152 ligand (CD152L)) expression. Both ICOSL and CD152L were up-regulated on monocytes by IFN-{gamma} but by distinct signaling pathways. Unlike CD152L expression, ICOSL expression did not change when monocytes were differentiated into dendritic cells (DCs) or after DCs were induced to mature by LPS, TNF-{alpha}, or CD40 ligation. Addition of ICOSIg to allogeneic MLRs between DCs and T cells reduced T cell proliferative responses but did so less efficiently than CTLA4Ig (CD152Ig) did. Similarly, ICOSIg also blocked Ag-specific T cell proliferation to tetanus toxoid. Thus, ICOSL, like CD80/86, is expressed on activated monocytes and dendritic cells but is regulated differently and delivers distinct signals to T cells that can be specifically inhibited by ICOSIg.

Keywords: Recombinant Fusion Proteins, Protein Binding, Monocytes, Monoclonal Antibodies, Membrane Glycoproteins, Lymphocyte Activation, Ligands, Inducible T-Cell Co-Stimulator Protein, Immunosuppressive Agents, Immunoconjugates, Differentiation Antigens, Dendritic Cells, Cultured Tumor Cells, CTLA-4 Antigen, COS Cells, CD3 Antigens, CD80 Antigens, CD86 Antigens, CD4-Positive T-Lymphocytes, Cell Line, CD28 Antigens, CD14 Antigens, CD Antigens, B-Lymphocytes, Abatacept, Solubility, T-Lymphocyte Differentiation Antigens, T-Lymphocyte Epitopes, Animals

Type: Article

PubMed: 10779774
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