Fc Receptors Overview

Fc receptors (Fc Receptors) are a class of proteins that exist on the surface of immune cells. Their function is to recognize and bind to the Fc part of antibodies, thereby mediating the activation, regulation and effect of various immune cells. These receptors play an important role in immune responses, inflammatory responses, and antibody therapy.

Fc receptors can be divided into different classes according to their structure and affinity, such as IgG receptors (including FcγRI, FcγRII, FcγRIII), IgE receptors (FcεRI) and IgA receptors (FcαRI). They are differentially expressed in different immune cells, such as macrophages, dendritic cells, natural killer cells and mast cells.

Fc receptors, by binding to the Fc portion of antibodies, trigger signal transduction pathways leading to the activation or regulation of immune cells. Activated Fc receptors can mediate immune effects such as phagocytosis, cytotoxicity, and proinflammatory responses, thereby eliminating pathogens and abnormal cells. Regulatory Fc receptors can regulate the activity of immune cells and maintain immune balance.

In addition to their important role in innate immune responses, Fc receptors also play a key role in antibody therapy. After the antibody binds to the antigen on the surface of tumor cells, it activates immune cells by binding to Fc receptors, promotes cytotoxicity, and then enhances the therapeutic effect of the antibody.

Research area of Fc Receptors

The research field of Fc receptors is very extensive, covering many important biological and medical fields. The following are some of the research areas of Fc receptors:

1. Immunology: Fc receptors play a key role in the immune response. Researchers are committed to understanding the functions, regulatory mechanisms of different Fc receptors and their roles in immune cell activation, cell signal transduction and immune regulation. This includes studies of Fc receptor-mediated cytotoxicity, phagocytosis, activation of immune cells, and antibody-dependent immune responses.
2. Antibody engineering and antibody therapy: The interaction between Fc receptors and antibodies is a key factor in antibody therapy. Researchers are committed to understanding the interaction between different Fc receptors and different types of antibodies in order to optimize the structure and function of antibodies and improve the efficacy and safety of antibody therapy. In addition, the polymorphisms of Fc receptors and the effect of gene polymorphisms on the response to antibody therapy were investigated.
3. Autoimmune and inflammatory diseases: Fc receptor dysfunction is closely related to the occurrence and development of various autoimmune and inflammatory diseases. Researchers are committed to exploring the association of Fc receptors with autoimmune diseases and investigating strategies to modulate Fc receptor signaling for the development of new treatments and drugs.
4. Immunological detection and diagnosis: The specificity of Fc receptors and the ability to bind to specific antibodies are widely used in the field of immunological detection and diagnosis. Researchers use Fc receptors to develop highly sensitive and specific immunoassays for detecting antibodies, cell surface markers, and immune reaction products.
5. New drug research and development: Fc receptors as drug targets have also attracted widespread attention. Researchers are committed to developing new drugs targeting Fc receptors to regulate the activity of immune cells and immune responses for the treatment of immune-related diseases, cancer and infectious diseases.

Fc Receptors: Key Players in Immune Cell Function

FcγRI (CD64): FcγRI is a high-affinity receptor for IgG and is widely expressed on macrophages, dendritic cells and some NK cells. It mediates antibody-dependent cellular cytotoxicity (ADCC) and phagocytosis, and is important for immune cell activation and the efficacy of antibody therapy.

FcγRII (CD32): The FcγRII family includes multiple subtypes (FcγRIIA, FcγRIIB, FcγRIIC) and is expressed in a variety of immune cells. FcγRIIA mediates ADCC and phagocytosis, while FcγRIIB is an inhibitory receptor that plays an important role in immune cell activation and immune homeostasis.

FcγRIII (CD16): The FcγRIII family also has multiple isoforms (FcγRIIIA, FcγRIIIB), which are expressed on natural killer cells and some other immune cells. FcγRIIIA mediates ADCC and plays a key role in antibody-dependent cytotoxicity, while FcγRIIIB is mainly expressed on neutrophils.

FcεRI (CD23): FcεRI is the receptor for IgE expressed on mast cells and basophils. It mediates allergic reactions and IgE-mediated immune responses, and plays an important role in allergic diseases and parasitic infections.

IgA Fc receptor

IgE Fc receptor

Fc receptor-like

IgG Fc receptor

IgA & IgM Fc receptors

References:

[1] Ben Mkaddem S, Benhamou M, Monteiro RC. Understanding Fc Receptor Involvement in Inflammatory Diseases: From Mechanisms to New Therapeutic Tools. Front Immunol. 2019;10:811. Published 2019 Apr 12. doi:10.3389/fimmu.2019.00811 https://pubmed.ncbi.nlm.nih.gov/31057544/