부산대학교 도서관

Summary: Memory B cells (MBCs) are an essential part of our immunological memory. They respond fast upon re-encountering pathogens and can differentiate into plasma cells that secrete protective antibodies. The focus of this review is on MBCs that lack, or express low levels of, CD21, hereafter referred to as CD21–/low. These cells are expanded in peripheral blood with age and during chronic inflammatory conditions such as viral infections, malaria, common variable immunodeficiency, and autoimmune diseases. CD21–/low MBCs have gained significant attention; they produce disease-specific antibodies/autoantibodies and associate with key disease manifestations in some conditions. These cells can be divided into subsets based on classical B-cell and other markers, e.g. CD11c, FcRL4, and Tbet which, over the years, have become hallmarks to identify these cells. This has resulted in different names including age-associated, autoimmune-associated, atypical, tissue-like, tissue-resident, tissue-restricted, exhausted, or simply CD21–/low B cells. It is however unclear whether the expanded 'CD21–/low' cells in one condition are equivalent to those in another, whether they express an identical gene signature and whether they have a similar function. Here, we will discuss these issues with the goal to understand whether the CD21–/low B cells are comparable in different conditions. CD21-/low memory B cells are expanded with age in healthy individuals and in patients with viral infections and autoimmune conditions and are associated with pathogen-specific antibodies as well as key disease manifestations. Depending on condition, CD21-/low memory B cells have been termed age-associated, autoimmune-associated, atypical, tissue-like, tissue-resident, tissue-restricted, exhausted or simply CD21-/low B cells. CD21-/low memory B cells are often CD27-IgD-CD11c+ and in some conditions they express Tbet, in others FcRL4 and in yet others both. [ABSTRACT FROM AUTHOR]