Costimulatory effect of B7-H1 on T-cell growth.

(A) The costimulatory effect of the B7-H1 is dose dependent. NW-purified T cells were cultured with the indicated doses of immobilized mB7-H1Ig (▪) or control immunoglobulin (○) in the presence of a suboptimal dose (200 ng/mL) of precoated anti-CD3 mAb. The proliferation of T cells was determined by ³H-thymidine incorporation assay. (B) B7-H1 costimulation is CD28 independent. NW-purified T cells obtained from spleens of wild-type (wt, left panel) and CD28^−/− (right panel) mice were cultured with control immunoglobulin (○), anti-CD28 mAb (▵), or mB7-H1Ig (▪) at 10 μg/mL in the presence of suboptimal doses (0.125 and 0.25 μg/mL) of immobilized anti-CD3. The proliferation of T cells was determined by³H-TdR incorporation assay. (C) B7-H1 preferentially costimulates CD4⁺ T-cell growth. Affinity-purified CD4⁺ or CD8⁺ T cells were cultured in the presence of a suboptimal dose of anti-CD3 and immobilized B7-H1Ig. Control Ig, ■; B7-H1Ig, ▪. The proliferation of T cells was determined by ³H-TdR incorporation assay. Data represent one experiment of 3 and ³H-TdR incorporation in counts per minute (cpm) ± SD.