Typically, these B cells are categorized as regulatory B cells, or bregs.139 Ming-Ming Shao et al.140 observed an increase of CD19+CD24hiCD27+ Bregs in Malignant pleural effusion (MPE) of lung cancer compared with that in blood, while the CD19+CD27‒IgD+ naive B cells showed a significant decrease compared with that in blood. Here, CD19 is linked to lung cancer.