Table 1.

Main B cells types, functions, and expression biomarkers.

Type of B Cells	Functions	Markers
Transitional B Cells	These cells link immature B cells in the bone marrow and mature B cells in lymphoid organs. These cells have differentiated into B cells from typical myeloid progenitor cells in the bone marrow; however, they are not yet mature.	These are characterized by IgM and IgD expression, by the high expression of CD24 and CD38, and by the absence of the memory marker CD27.
Naïve B Cells	Naïve B cells are located in the secondary lymphoid organs. They are mature but not yet activated. Naive B lymphocytes can differentiate into plasmablasts and plasma or memory B cells in response to stimulation by specific antigens.	These cells have phenotypic markers CD24+CD38+CD27−.
Plasmablasts and Plasma Cells	Plasma cells are long-lived differentiated cells whose function is the production of antibodies. Plasmablasts are also antibody-producing cells, but unlike plasma cells, they are short-lived. Plasma cells migrate to the bone marrow, where they continue to produce antibodies to protect against re-infection.	Phenotypically, plasmablasts and plasma cells are characterized by the absence of CD20 expression and the high expression of CD38.
Memory B Cells	Memory B cells continually recirculate around the periphery and rapidly differentiate into antibody-producing plasmablasts upon interaction with T cells after specific antigen recognition. This memory B response is characterized by being more potent towards antigens than the primary B responses and producing responses with greater affinity and the isotype change of immunoglobulins.	These cells phenotypically express CD20+, CD27+, CD38−.