Function and Regulation of Age‐Associated B Cells in Diseases

ABSTRACT The aging process often leads to immune‐related diseases, including infections, tumors, and autoimmune disorders. Recently, researchers identified a special subpopulation of B cells in elderly female mice that increases with age and accumulates prematurely in mouse models of autoimmune diseases or viral infections; these B cells are known as age‐related B cells (ABCs). These cells possess distinctive cell surface phenotypes and transcriptional characteristics, and the cell population is widely recognized as CD11c + CD11b + T‐bet + CD21 ‐ CD23 ‐ cells. Research has shown that ABCs are a heterogeneous group of B cells that originate independently of the germinal center and are insensitive to B‐cell receptor (BCR) and CD40 stimulation, differentiating and proliferating in response to toll‐like receptor 7 (TLR7) and IL‐21 stimulation. Additionally, they secrete self‐antibodies and cytokines to regulate the immune response. These issues have aroused widespread interest among researchers in this field. This review summarizes recent research progress on ABCs, including the functions and regulation of ABCs in aging, viral infection, autoimmune diseases, and organ transplantation.