FcRezeptorvermittelte

Fc receptor-mediated refers to cellular processes initiated when the constant (Fc) region of an antibody binds to Fc receptors on various immune and non-immune cells. This interaction translates antibody recognition of antigen into effector responses such as phagocytosis, cytotoxicity, degranulation, cytokine production, and antigen presentation. Fc receptors are diverse and subclass-specific; in humans the main families are Fcγ receptors for IgG (including FcγRI/CD64, FcγRII/CD32 with isoforms IIa, IIb, IIc, and FcγRIII/CD16), Fcε receptors for IgE ( FcεRI, high affinity on mast cells, basophils; FcεRII/CD23 on B cells), and Fcα receptors for IgA ( FcαRI/CD89). Signaling is controlled by activating ITAM-bearing receptors and the inhibitory ITIM-containing FcγRIIB, allowing tuning of responses.

Key effector mechanisms include opsonization-driven phagocytosis by macrophages and neutrophils, antibody-dependent cellular cytotoxicity (ADCC) by NK cells via FcγRIII, and mast cell/basophil degranulation upon IgE-FcεRI engagement. Immune complexes can be cleared by liver and spleen macrophages through Fc receptors, and dendritic cells can present immune-complex-derived antigens to T cells. The balance of activating and inhibitory signals, receptor expression patterns, and context of antigen exposure determine the outcome—protection or pathology.

Clinical relevance includes therapeutic antibodies designed to engage Fc receptors to mediate ADCC, vaccines and IVIG effects, and autoimmune disease mechanisms where Fc receptor signaling contributes to inflammation. Receptor repertoires vary among species and tissues, influencing immune responses and therapeutic efficacy.