FCGR3B

FCGR3B (Fc gamma receptor IIIb) is a gene that encodes a low-affinity receptor for the Fc region of IgG antibodies. It is primarily expressed on neutrophils, a type of white blood cell critical for the innate immune system. Unlike its related gene, FCGR3A, FCGR3B lacks a transmembrane domain. Instead, it is anchored to the cell membrane via a glycosylphosphatidylinositol (GPI) linkage.

Functionally, FCGR3B plays a role in neutrophil activation and antibody-mediated immune responses. When IgG antibodies bind to antigens (e.g., pathogens), the Fc regions of these antibodies can interact with FCGR3B on neutrophils. This interaction can trigger various cellular responses, including phagocytosis (engulfment and destruction of pathogens), the release of inflammatory mediators, and the generation of reactive oxygen species.

Genetic variations in FCGR3B are associated with susceptibility to various autoimmune and infectious diseases. For example, copy number variations (CNVs) in FCGR3B have been linked to systemic lupus erythematosus (SLE) and other autoimmune disorders. Individuals with lower copy numbers of FCGR3B may have a reduced ability to clear immune complexes, leading to increased inflammation and tissue damage. Conversely, higher copy numbers may provide some protection against certain infections.

Due to its role in immune function and its association with disease susceptibility, FCGR3B is an important area of research in immunology and genetics. Further studies are needed to fully elucidate the complex mechanisms by which FCGR3B influences immune responses and disease pathogenesis.