S1 Table. Dataset of AIGA+ and HC plasma samples tested by indirect ELISA, cell-based assay and cELISA.

S2 Table. Dataset for sensitivity and specificity analysis of cell-based assay and cELISA using ROC analysis. S1 Fig. Flow cytometry gating strategy for determination of MHC class II expression in THP-1 cells. A representative gating strategy is shown for THP-1 cells under three conditions: no plasma, healthy control (HC), and AIGA-positive (AIGA⁺). THP-1 cells were first identified based on forward scatter height (FSC-H) and side scatter height (SSC-H) properties to exclude debris. Doublets were then removed by FSC-A versus FSC-H gating to define singlets. MHC class II–positive cells were subsequently identified based on FITC fluorescence intensity (Comp-FL1-H). The mean fluorescence intensity (MFI) of MHC class II–positive cells was used to calculate percentage inhibition. S1 Experiment. Assay specificity validation of cELISA. S1 Text. Assay performance of indirect ELISA. (ZIP)

附表2：采用受试者工作特征（Receiver Operating Characteristic, ROC）分析的细胞测定法与竞争性酶联免疫吸附试验（cELISA）灵敏度及特异性分析数据集。图S1：THP-1细胞中主要组织相容性复合体II（Major Histocompatibility Complex class II, MHC class II）表达检测的流式细胞术设门策略。该图展示了三种培养条件下THP-1细胞的代表性设门方案：无血浆组、健康对照（Healthy Control, HC）组以及AIGA阳性（AIGA⁺）组。首先通过前向散射光高度（Forward Scatter Height, FSC-H）与侧向散射光高度（Side Scatter Height, SSC-H）特征识别THP-1细胞，以排除细胞碎片；随后通过前向散射光面积（Forward Scatter Area, FSC-A）与前向散射光高度（FSC-H）的设门去除细胞聚集体，以获取单细胞群体；继而基于异硫氰酸荧光素（Fluorescein Isothiocyanate, FITC）荧光强度（补偿后FL1通道高度，Comp-FL1-H）识别MHC II类阳性细胞。以MHC II类阳性细胞的平均荧光强度（Mean Fluorescence Intensity, MFI）计算抑制率百分比。实验S1：竞争性酶联免疫吸附试验（cELISA）的测定特异性验证。文本S1：间接酶联免疫吸附试验的测定性能。(ZIP)