T-cell response to β₂GPI/PS in bulk PBMC cultures supplemented with FBS, autologous APS plasma, or healthy control plasma. (A) PBMCs from APS4 were cultured in triplicate with or without antigens, including MalBP, GP-F, β₂GPI, PS, and β₂GPI/PS, in medium supplemented with FBS, autologous APS plasma, or healthy control plasma. The antigen-induced T-cell proliferative response was assessed by ³H-thymidine incorporation. Results are shown as mean (column) and standard deviation (error bar) of triplicate measurements. Analogous findings were obtained in 7 independent experiments in PBMCs from all 5 patients with APS. (B) β₂GPI/PS-specific T-cell response in PBMC cultures of APS4 in medium supplemented with 2 different lots of FBS (no. 1 and no. 2), plasma samples from 4 APS patients (APS1, 3, 4, and 9), or plasma samples from 3 healthy donors (HD1, 2, and 3). β₂GPI/PS-specific T-cell response was expressed as a β₂GPI/PS-to-PS ratio, which was the mean cpm incorporated in the triplicate culture with β₂GPI/PS divided by the mean cpm incorporated in the triplicate culture with PS alone (standard deviations for the individual results were within 20% of the mean in all cases). Similar results were obtained from 3 additional patients with APS (APS1, APS3, and APS9).