Costimulation of T cells by B7-H2, a B7-like molecule that binds ICOS

This report describes a new human B7-like gene designated B7-H2, Cell surfa ce expression of B7-H2 protein is detected in monocyte-derived immature den dritic cells. Soluble B7-H2 and immunoglobulin (Ig) fusion protein, B7-H21g , binds activated but not resting T cells and the binding is abrogated by i nducible costimulator Ig (ICOSIg), but not CTLA41S. In addition, ICOSIg sta ins Chinese hamster ovary cells transfected with B7-H2 gene. By suboptimal cross-linking of CD3, costimulation of T-cell proliferation by B7-H21g is d ose-dependent and correlates with secretion of interleukin (IL)-2, whereas optimal CD3 ligation preferentially stimulates IL-10 production. The result s indicate that B7-H2 is a putative ligand for the ICOS T-cell molecule. (C ) 2000 by The American Society of Hematology.