An agonist human ICOS monoclonal antibody that induces T cell activation and inhibits proliferation of a myeloma cell line

The inducible costimulator (ICOS), the third member of the CD28/CD152 receptor family, is an important costimulatory molecule during the immune response. In this study, a functional anti-human ICOS MAb 2C7 was obtained. The specificity of this MAb was verified by flow cytometry, Western blotting, and competition with anti-ICOS MAb ISA3. This MAb could well recognize ICOS molecule expressed on activated T cells and induce the activation as well as proliferation of T cells prestimulated by anti-human CD3 MAb. Furthermore, we found that MAb 2C7 could induce the growth arrest of XG2 cells, a human multiple myeloma cell line, which abnormally expressed ICOS molecule, and led to its apoptosis after 48 h of treatment. This functional anti-human ICOS MAb provides a valuable tool for further study of biological functions as well as signal transduction of ICOS/GL50.