B-cell

B cells are lymphocytes derived from hematopoietic stem cells in bone marrow that play central roles in adaptive immunity through both antibody production and antigen presentation. These cells are characterized by the expression of B cell receptors (BCRs) and major histocompatibility complex (MHC) class II molecules, enabling them to recognize antigens and present processed peptide fragments to T cells. During immune responses, B cells undergo clonal expansion and differentiation into plasma cells that synthesize antibodies, or into memory cells that provide long-lived protective immunity. Their developmental progression includes transition through germinal centers within lymphoid tissues, where B cells interact with follicular helper T cells and undergo somatic hypermutation and class switching to generate functionally diverse antibody isotypes.

Beyond antibody production, B cells function as professional antigen-presenting cells (APCs) that regulate immune responses through direct interactions with T cells via co-stimulatory molecules such as CD86 and ICOSL, and through modulation of inflammatory microenvironments in lymph nodes and tertiary lymphoid structures. Distinct B cell subsets—including classical and atypical B cells—exhibit specialized roles in tissue-resident immunity and systemic immune control, with genetic variants affecting B cell-specific gene expression contributing to susceptibility for autoimmune, infectious, and neurodegenerative diseases. The therapeutic targeting of B cells has proven effective in multiple disease contexts including autoimmune conditions and cancer, underscoring their importance as both central effectors of protective immunity and drivers of pathological inflammation when dysregulated.