Binding of β₂GPI to anionic PL facilitates the processing and presentation of p276-290, which activates p276-290–reactive T-cell lines. (A) Autologous immature DCs were pulsed with or without a mixture of native β₂GPI and various PL liposomes (▪ and □, respectively), induced to mature, and used to stimulate the p276-290–reactive T-cell line KS3. The antigen-induced T-cell response was evaluated by [³H]thymidine incorporation. A representative result from 2 independent experiments is shown. (B) Autologous immature DCs were pulsed with or without a mixture of native β₂GPI and various PL liposomes (▪ and □, respectively), induced to mature, and used to stimulate the p276-290–reactive T-cell line KS3. The antigen-induced T-cell response was evaluated by IFN-γ production. A representative result from 3 independent experiments is shown. (C) The capacity of individual PLs to bind β₂GPI was evaluated by a solid-phase assay. A representative result from 2 independent experiments is shown. OD indicates optical density. (D) The p276-290–reactive T-cell line OM-b was cultured with autologous DCs bearing DOPS-bound β₂GPI in the presence or absence of chloroquine, brefeldin A, anti–HLA-DR mAb, or control mAb. The antigen-induced T-cell response was evaluated by IFN-γ production. Results are shown as the mean and standard deviation. A representative result from 2 independent experiments is shown.