Interleukin 17 (IL-17) is a pro-inflammatory cytokine that plays a critical role in host defense against infections and in the pathogenesis of several infectious diseases. This cytokine is primarily produced by a subset of CD4+ T cells known as Th17 cells, although other cells such as CD8+ T cells and certain innate immune cells can also produce IL-17. Understanding the role of IL-17 in infectious diseases is crucial for developing targeted therapies and improving patient outcomes.
What is the role of IL-17 in the immune response?
IL-17 is central to the immune response against various pathogens, particularly extracellular bacteria and fungi. It acts by stimulating the production of antimicrobial peptides, enhancing neutrophil recruitment, and promoting the production of pro-inflammatory cytokines and chemokines. These actions collectively help in containing and eliminating pathogens. The
IL-17 pathway is essential for maintaining the integrity of epithelial barriers, especially in the skin, gut, and respiratory tract.
How does IL-17 contribute to infectious disease pathogenesis?
While IL-17 is protective in many contexts, its dysregulation can contribute to the pathogenesis of infectious diseases. Excessive or prolonged production of IL-17 can lead to tissue damage and chronic inflammation. For instance, in
chronic infections such as tuberculosis and HIV, IL-17 may exacerbate inflammation, leading to tissue damage. Additionally, in autoimmune conditions with infectious triggers, such as psoriasis and rheumatoid arthritis, IL-17 can amplify disease pathology.
Which infectious diseases are associated with IL-17?
IL-17 has been implicated in a variety of infectious diseases. In bacterial infections, such as
Staphylococcus aureus and
Klebsiella pneumoniae, IL-17 is crucial for neutrophil-mediated clearance. In fungal infections like
Candida albicans, IL-17 helps in recruiting immune cells to the site of infection. Viral infections, including
HIV and
influenza, also interact with the IL-17 pathway, although the outcomes can be variable depending on the context and stage of infection.
What are the therapeutic implications of targeting IL-17?
Given its dual role in host defense and disease pathogenesis, targeting IL-17 presents both opportunities and challenges.
Biologic therapies that inhibit IL-17 or its receptor are currently used in treating autoimmune diseases like psoriasis and ankylosing spondylitis. However, in infectious diseases, the therapeutic use of IL-17 inhibitors needs careful consideration to avoid impairing host defense. On the other hand, enhancing IL-17 responses might be beneficial in cases where the immune response is inadequate, such as in certain chronic infections.
What are the challenges in studying IL-17?
Research on IL-17 faces several challenges, including its context-dependent effects. The
pleiotropic nature of IL-17 means that its effects can vary widely depending on the type of pathogen, the site of infection, and the host's immune status. Additionally, the redundancy and overlap in the cytokine network can complicate the assessment of IL-17’s specific role in disease. There is also a need for more precise tools and models to study IL-17 in human infectious diseases.
Future directions in IL-17 research and infectious diseases
Future research on IL-17 in infectious diseases is likely to focus on elucidating its precise mechanisms of action and identifying biomarkers that predict responses to IL-17-targeted therapies. Understanding the interplay between IL-17 and other components of the immune system, such as the
microbiome and other immune cells, could provide insights into novel therapeutic strategies. Additionally, exploring the role of IL-17 in emerging infectious diseases and its potential as a target for vaccine adjuvants are promising areas of investigation.
Overall, IL-17 is a pivotal cytokine in the context of infectious diseases, with a complex role that balances host protection and inflammation-driven pathology. Continued research will be essential to harness its potential for therapeutic benefit while minimizing risks.
