CD64

CD64, also known as Fc gamma receptor I (FcγRI), is a transmembrane protein belonging to the immunoglobulin superfamily. It is a high-affinity receptor for the Fc portion of immunoglobulin G (IgG) antibodies. CD64 is primarily expressed on myeloid cells, including monocytes, macrophages, and dendritic cells, with lower levels found on neutrophils and eosinophils. Its expression can be significantly upregulated by cytokines, particularly interferon-gamma (IFN-γ), which is crucial for mounting effective immune responses.

The primary function of CD64 is to mediate antibody-dependent cellular phagocytosis (ADCP) and antibody-dependent cellular cytotoxicity (ADCC). When IgG antibodies bind to antigens on the surface of pathogens or target cells, CD64 on myeloid cells can bind to the Fc region of these antibodies. This binding triggers intracellular signaling pathways that lead to the engulfment and destruction of the antibody-coated target. This mechanism is essential for clearing infections and eliminating abnormal cells.

CD64 plays a vital role in innate immunity by bridging the gap between adaptive and innate immune responses. It allows immune cells to recognize and respond to antibody-opsonized targets, enhancing their effector functions. Dysregulation or deficiency in CD64 function can impair the immune system's ability to combat infections. Furthermore, CD64 is a target for therapeutic interventions, particularly in autoimmune diseases and cancer immunotherapy, where modulating its activity can influence immune responses. Research continues to explore the multifaceted roles of CD64 in various physiological and pathological conditions.