Immune Cell Profiling of COVID-19 Patients in the Recovery Stage by Single-Cell Sequencing

Wen Wen; Wenru Su; Hao Tang; Wenqing Le; Xiaopeng Zhang; Yingfeng Zheng; XiuXing Liu; Lihui Xie; Jianmin Li; Jinguo Ye; Xiuliang Cui; Yushan Miao; Depeng Wang; Jiantao Dong; Chuan-Le Xiao; Wei Chen; Hongyang Wang

Using sc-BCR-seq to assess the status of clonal expansions in the blood of patients, we found that IL4R + naïve B cells showed little clonal expansion, whereas CD27 + CD38 + memory B cells showed the highest expansion levels among diverse B cell subsets (Fig. 6A) . At the individual level, we found that COVID-19 patients had significantly expanded clones compared to that in the HCs, supporting the assumption that B cells had experienced unique clonal VDJ rearrangements under SARS-CoV-2 infection. We also found that a higher B cell clonality consistently remained in the ERS compared with that in the LRS patients (Fig. 6B) . Moreover, quantification of the most highly expanded (maximum) clone for each subject showed that the ratios of the maximum clones were higher in the ERS group than in the HCs (Fig. 6C) . To understand the functional status of expanded cloned B cells, we performed DEG analysis between the cloned memory B cells and the other B cells.