Fc receptors

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Fc receptor binding, schematic representation

Fc receptors are membrane receptors for different immunoglobulin isotypes . All molecules except the FcRn receptor belong to the immunoglobulin superfamily . The name is based on the binding specificity of the receptors to a part of the C terminus of an antibody which Fc fragment (engl. Fragment crystallisable ) is called and the constant region of an antibody. Fc receptors are glycosylated . It is mainly formed by myeloid cells of the immune system . According to their protein structure , they can be divided into two groups. According to their affinity , they are divided into five subtypes, which are named according to their bound immunoglobulin.

Types

Fcα receptor (synonymous CD89) binds the Fc domain of IgA . The receptor can be found on the surface of monocytes , macrophages , neutrophils and eosinophils .

The Fcγ receptors bind the Fc domain of IgG . They are found on the surface of phagocytes , B lymphocytes , NK cells, and dendritic cells . These receptors can recognize and bind aggregated IgG molecules. The binding triggers different reactions depending on the cell type: e.g. B. Opsonization or ADCC (by NK cells). There are different structural types of the Fcγ receptor (FcγRI or CD64 , FcγRII or CD32 and FcγRIII or CD16 ).

The Fcε receptors bind the Fc domain of free IgE . They can be found on the surface of mast cells and basophils . The mast cell is activated by the binding of antigens to these bound antibodies . This process plays a decisive role in type I allergies . A distinction is made between two types of Fcε receptors in mammals, FcεRI with high affinity and FcεRII with low affinity for IgE.

Fcμ receptors bind the Fc domain of IgM .

The neonatal Fcγ receptor (FcRn) belongs to the MHC superfamily and binds IgG with weak affinity.

TRIM21 binds Fc regions of IgG, IgA and IgM in the course of intracellular antibody-mediated degradation . Bacterial Fc-binding proteins are protein A and protein G .

Individual evidence

  1. ↑ Marc Daëron: Fc Receptors. Springer, 2014, ISBN 978-3-319-07911-0 . P. 4.
  2. ↑ JM Hayes, EF Cosgrave, WB Struwe, M. Wormald, GP Davey, R. Jefferis, PM Rudd: Glycosylation and Fc receptors. In: Current topics in microbiology and immunology. Volume 382, ​​2014, pp. 165-199, doi : 10.1007 / 978-3-319-07911-0_8 , PMID 25116100 .
  3. ↑ JM Hayes, EF Cosgrave, WB Struwe, M. Wormald, GP Davey, R. Jefferis, PM Rudd: Glycosylation and Fc receptors. In: Current topics in microbiology and immunology. Volume 382, ​​2014, pp. 165-199, doi : 10.1007 / 978-3-319-07911-0_8 , PMID 25116100 .
  4. Jump up ↑ A. Pincetic, S. Bournazos, DJ DiLillo, J. Maamary, TT Wang, R. Dahan, BM Fiebiger, JV Ravetch: Type I and type II Fc receptors regulate innate and adaptive immunity. In: Nature Immunology . Volume 15, Number 8, August 2014, pp. 707-716, doi : 10.1038 / ni.2939 , PMID 25045879 .