Functional aspects of B7-H1-expressing blasts from patients. (A) Cell cycle of purified CD34⁺ blasts as a function of B7-H1 expression. Freshly isolated blasts that markedly expressed B7-H1 molecules (from patient no. 36) and blasts cultured with IFNγ and TNFα to induce B7-H1 expression (from patient no. 10 and patient no. 40) were analyzed. B7-H1⁺ (■) and B7-H1⁻ (□) cells are indicated. (B) B7-H1–expressing patient blasts were cultured with normal T cells in the presence of control IgG or anti–B7-H1 monoclonal antibodies or medium alone. Data are mean (and SD) of 3 experiments; in each experiment using a different patient sample, data labeled control IgG were defined as 100%. *P = .026 compared with control IgG.