IFN-γ

Definition

IFN-γ, or interferon gamma, is a cytokine that plays a crucial role in the immune response, particularly in enhancing the ability of immune cells to fight infections and regulate immune functions. It is produced primarily by T cells and natural killer (NK) cells and acts as a potent activator of macrophages, promoting the clearance of intracellular pathogens. In the context of disruptions in the immune system, IFN-γ can be involved in both protective and pathological responses, influencing autoimmune diseases and chronic inflammation.

5 Must Know Facts For Your Next Test

1. IFN-γ is essential for the activation of macrophages, which enhances their ability to destroy pathogens and presents antigens to T cells.
2. Excessive or unregulated production of IFN-γ can contribute to autoimmune diseases by promoting inflammation and tissue damage.
3. In viral infections, IFN-γ helps to enhance the antiviral response by activating NK cells and promoting the expression of MHC class I molecules on infected cells.
4. IFN-γ also has a role in regulating the balance between different T cell subsets, influencing whether a Th1 or Th2 immune response is favored.
5. Therapeutically, IFN-γ has been explored for its potential in treating various diseases, including chronic infections and certain types of cancer.

Review Questions

• How does IFN-γ enhance the immune response against intracellular pathogens?
  • IFN-γ enhances the immune response by activating macrophages, which improves their ability to engulf and destroy intracellular pathogens. It also promotes antigen presentation by increasing the expression of MHC class II molecules on macrophages. Furthermore, IFN-γ stimulates the production of reactive oxygen species and other effector molecules that help in killing infected cells, thereby bolstering both innate and adaptive immunity.
• What are the implications of excessive IFN-γ production in autoimmune diseases?
  • Excessive production of IFN-γ can lead to heightened inflammation and contribute to tissue damage in autoimmune diseases. This cytokine can promote an imbalance between immune responses, favoring a Th1 response that attacks self-tissues. Such overactivity can exacerbate conditions like rheumatoid arthritis or multiple sclerosis, where immune cells mistakenly target healthy tissues as if they were pathogens.
• Evaluate how IFN-γ can both protect against infections and contribute to chronic inflammation. What mechanisms are involved?
  • IFN-γ plays a dual role by protecting against infections through its activation of macrophages and enhancement of cellular immunity while also contributing to chronic inflammation when produced excessively. Mechanisms include its ability to recruit more immune cells to sites of infection, thus amplifying responses. However, chronic exposure can lead to sustained inflammation, damaging healthy tissues and perpetuating inflammatory cycles often seen in autoimmune disorders or chronic infections. This highlights the importance of tightly regulating IFN-γ levels for maintaining immune balance.

Related terms

Cytokine: A broad category of small proteins that are important in cell signaling, especially in the immune system, and can influence the behavior of other cells.

Macrophage: A type of white blood cell that engulfs and digests cellular debris, foreign substances, and pathogens, playing a critical role in immune defense.

Th1 Cells: A subset of T helper cells that produce IFN-γ and are primarily involved in promoting cell-mediated immunity against intracellular pathogens.