key term - FcγRI

Definition

FcγRI, also known as CD64, is a high-affinity Fc receptor that binds to the Fc region of immunoglobulin G (IgG) antibodies. It plays a crucial role in the recognition and phagocytosis of pathogens by immune cells, particularly macrophages and neutrophils.

5 Must Know Facts For Your Next Test

1. FcγRI has the highest affinity for the Fc region of IgG antibodies among the Fc gamma receptor family.
2. Binding of IgG-opsonized pathogens to FcγRI on the surface of macrophages and neutrophils triggers phagocytosis and the destruction of the target.
3. FcγRI expression is upregulated in response to inflammatory cytokines, such as interferon-gamma (IFN-γ), enhancing the phagocytic capacity of immune cells.
4. Engagement of FcγRI can also activate other immune functions, including the release of inflammatory mediators and the generation of reactive oxygen species.
5. Dysregulation of FcγRI expression or function has been implicated in the pathogenesis of various autoimmune and inflammatory disorders.

Review Questions

• Explain the role of FcγRI in pathogen recognition and phagocytosis.
  • FcγRI, a high-affinity Fc receptor, plays a crucial role in the recognition and phagocytosis of pathogens by immune cells. When IgG antibodies bind to the surface of a pathogen, the Fc region of the antibody can be recognized by FcγRI expressed on the surface of macrophages and neutrophils. This binding triggers the phagocytosis of the opsonized pathogen, leading to its engulfment and subsequent destruction by the immune cell. The high affinity of FcγRI for the Fc region of IgG antibodies enhances the efficiency of this process, allowing for the effective clearance of antibody-coated pathogens.
• Describe how the expression of FcγRI is regulated and how it impacts the phagocytic capacity of immune cells.
  • The expression of FcγRI is upregulated in response to inflammatory cytokines, such as interferon-gamma (IFN-γ). This increased expression of FcγRI on the surface of macrophages and neutrophils enhances the phagocytic capacity of these immune cells. When more FcγRI receptors are present, the binding of IgG-opsonized pathogens is more efficient, leading to a greater rate of phagocytosis and the subsequent destruction of the target. This regulation of FcγRI expression is an important mechanism by which the immune system can adapt to different pathogenic challenges, increasing the phagocytic potential of key immune cells when needed.
• Analyze the potential implications of dysregulated FcγRI function in the context of autoimmune and inflammatory disorders.
  • Dysregulation of FcγRI expression or function has been implicated in the pathogenesis of various autoimmune and inflammatory disorders. For example, in autoimmune diseases, the overexpression or hyperactivation of FcγRI on immune cells can lead to the inappropriate recognition and phagocytosis of the body's own tissues, contributing to tissue damage and inflammation. Conversely, impaired FcγRI function may compromise the immune system's ability to effectively clear pathogens, increasing susceptibility to infections. Understanding the role of FcγRI in these disease processes is crucial for the development of targeted therapies that can modulate FcγRI activity and restore immune homeostasis, potentially alleviating the symptoms and progression of autoimmune and inflammatory disorders.

Related terms

Fc Receptor: Fc receptors are cell surface receptors that bind to the Fc region of antibodies, allowing immune cells to recognize and respond to antibody-coated targets.

Phagocytosis:

Phagocytosis is the process by which cells, such as macrophages and neutrophils, engulf and digest foreign particles, pathogens, or cellular debris.

Opsonization:

Opsonization is the process of coating a pathogen or particle with antibodies or complement proteins, making it more susceptible to phagocytosis by immune cells.