Studies on the interactions between SARS‐CoV‐2 and humoral immunity are fundamental to elaborate effective therapies including vaccines. We used polychromatic flow cytometry, coupled with unsupervised data analysis and principal component analysis (PCA), to interrogate B cells in untreated patients with COVID‐19 pneumonia. COVID‐19 patients displayed normal plasma levels of the main immunoglobulin classes, of antibodies against common antigens or against antigens present in common vaccines. However, we found a decreased number of total and naïve B cells, along with decreased percentages and numbers of memory switched and unswitched B cells. On the contrary, IgM⁺ and IgM⁻ plasmablasts were significantly increased. In vitro cell activation revealed that B lymphocytes showed a normal proliferation index and number of dividing cells per cycle. PCA indicated that B‐cell number, naive and memory B cells but not plasmablasts clustered with patients who were discharged, while plasma IgM level, C‐reactive protein, D‐dimer, and SOFA score with those who died. In patients with pneumonia, the derangement of the B‐cell compartment could be one of the causes of the immunological failure to control SARS‐Cov2, have a relevant influence on several pathways, organs and systems, and must be considered to develop vaccine strategies.

中文翻译：

---

COVID-19肺炎患者外周血成浆细胞的扩增和记忆B细胞的丢失。

对SARS-CoV-2与体液免疫之间相互作用的研究是制定包括疫苗在内的有效疗法的基础。我们使用多色流式细胞仪，结合无监督的数据分析和主成分分析（PCA），对未经治疗的COVID-19肺炎患者的B细胞进行询问。COVID-19患者显示出主要免疫球蛋白类别的正常血浆水平，针对常见抗原的抗体或针对针对普通疫苗中存在的抗原的抗体。然而，我们发现总的和纯朴的B细胞数量减少了，同时内存切换和未切换的B细胞的百分比和数量也减少了。相反，IgM抗体⁺和IgM ^-成浆细胞明显增加。体外细胞活化显示B淋巴细胞显示正常的增殖指数和每个周期的分裂细胞数量。PCA指出出院患者的B细胞数量，幼稚和记忆B细胞而非成浆细胞聚集，而死亡患者的血浆IgM水平，C反应蛋白，D二聚体和SOFA得分较高。在肺炎患者中，B细胞区室的混乱可能是控制SARS-Cov2的免疫学失败的原因之一，对几种途径，器官和系统都有相关影响，必须考虑制定疫苗策略。