Binding of B7-H2 to ICOS on activated T cells.

(A) Expression of the counter-receptor of B7-H2 on activated T cells. Resting (0 hour) and activated T cells were stained with B7-H2Ig (open) or control Ig (shaded) and analyzed by flow cytometry. T cells were activated with PHA (5 μg/mL) for the indicated times (24, 48, and 72 hours). (B) ICOSIg abrogates the binding of B7-H2 to activated T cells. Purified T cells were stimulated with 5 μg/mL PHA for 48 hours. Activated T cells were stained with control Ig (shaded) or 1 μg of B7-H2Ig (open) in the presence of buffer, ICOSIg (10 μg), or CTLA4Ig (10 μg) and analyzed by flow cytometry. (C) Binding of ICOSIg to cell surface B7-H2. CHO cells transfected with phB7-H2 (open) or parental vector (shaded) were stained with ICOSIg or anti-B7-H2 antibody and analyzed by flow cytometry.