Total RNAs were extracted from blood samples using PAXgene Blood RNA Kit (Qiagen, Cat. No. 762174) following the manufacturer's instructions. 2 μg total RNAs were used for the construction of sequencing libraries. About 2 μg total RNA of each sample were used for BCR sequencing. Library preparation using KC-DigitalTM Stranded BCR-seq Library Prep Kit for Illumina® 150 (Seqhealth Technology Co., Ltd., Wuhan, China, Cat. No. DT0815-02) following the manufacturer's instruction.