Fig. 4.

B7x has a putative counterreceptor on activated T cells distinct from CD28, CTLA-4, ICOS, and PD-1. (A) The 293 transfectants expressing CD28, ICOS, and PD-l or the DT230 transfectant expressing cell surface CTLA-4 were stained with B7x-Ig fusion protein (open histograms) or mouse IgG1 (shaded histograms) as a control, and were then stained with a PE-conjugate anti-mouse-IgG. All transfectants were also stained with specific mAbs (open histograms) or control Abs (shaded histograms). (B) DO11.10 T cell antigen receptor transgenic Th1 cells from WT or BTLA-/- mice were incubated with irradiated BALB/c spleen cells in the presence of 5 μg/ml OVA323-339 peptide for 4 days. Cells were then incubated with B7x-Ig (open histograms) or human IgG1 (shaded histograms) as a control and stained with a PE-conjugated anti-human-IgG.