Interleukin-6 Defends Against Influenza Virus by Boosting Antibody Response Not Inflammation
Nikhil Prasad Fact checked by:Thailand Medical News Team Feb 21, 2025 21 hours, 42 minutes ago
Medical News: Influenza is a serious respiratory virus that affects millions of people worldwide, leading to severe illness and even death in some cases. Scientists have long sought to understand how the immune system combats this virus, with a focus on the role of different immune molecules. A new study conducted by researchers at the Institute of Molecular Health Science, ETH Zurich, Switzerland, sheds light on how the immune system defends itself against influenza using a key molecule called Interleukin-6 (IL-6). Their findings reveal that IL-6 plays a crucial role in generating protective antibody responses, but contrary to popular belief, it does not drive the early inflammatory response often associated with severe flu cases.
Interleukin-6 Defends Against Influenza Virus by Boosting Antibody Response Not Inflammation
This
Medical News report highlights the key discoveries from the study and explains what they mean for our understanding of flu immunity and potential treatments.
IL6 Is Essential for a Strong Antibody Response
IL-6 is a multifunctional molecule that influences various aspects of the immune system. In the case of influenza infection, the study found that IL-6 helps the body produce virus-fighting antibodies. Researchers conducted experiments using genetically modified mice that lacked IL-6 or its receptor (IL-6R). These mice experienced worse flu symptoms and took longer to recover, compared to normal mice. They also had a reduced ability to clear the virus from their lungs.
The delay in recovery was traced back to a weakened production of antibodies. Specifically, the study showed that IL-6 is necessary for generating a type of immune cell called T follicular helper (Tfh) cells. These cells are crucial because they help B cells produce antibodies that target the influenza virus. Without IL-6, the mice struggled to mount a strong antibody response, making them more vulnerable to the infection.
IL6 Does Not Trigger Early Inflammation in the Lungs
Inflammation is a double-edged sword in flu infections. On one hand, it helps the immune system fight the virus, but excessive inflammation can damage lung tissue, leading to severe complications. Some previous studies suggested that IL-6 might contribute to this harmful inflammation, but the latest research challenges that idea.
Scientists observed that the absence of IL-6 did not significantly alter early inflammatory responses in the lungs. The recruitment of immune cells like neutrophils and macrophages - cells known for their role in inflammation - remained largely unchanged in IL-6-deficient mice. Likewise, levels of pro-inflammatory molecules such as TNF-alpha and interferons were not significantly affected.
The Complement System and IL6 Connection
Another key finding of the study was that IL-6 supports the production of complement proteins C3 and C5 in the lungs. The complement system is an important part of the immune response that helps identify and neutralize pathogens. Without IL-6,
the levels of these proteins were much lower, suggesting that IL-6 enhances immunity not only through antibody production but also through boosting complement-mediated defense.
Specific Cell Types and Their Response to IL6
To pinpoint which cells in the immune system rely on IL-6, researchers conducted additional experiments where they selectively removed IL-6 receptors from different types of immune cells. They found that removing IL-6 signaling from T cells, but not B cells or macrophages, impaired the production of Tfh cells and antibodies. This means that while IL-6 is not needed for every immune cell’s function, it is critical for T cells to support B cell-driven antibody responses.
Conclusion and Implications for Future Research
This study provides a deeper understanding of how IL-6 protects against influenza. It confirms that IL-6 is not responsible for the excessive inflammation often seen in severe flu cases, but rather, it plays a vital role in ensuring that the body can produce strong and effective antibodies. The findings suggest that targeting IL-6 for therapeutic purposes should be approached with caution. While some treatments aim to block IL-6 to reduce inflammation in diseases like COVID-19, this study indicates that IL-6 suppression could weaken the immune response against viral infections like influenza.
Future research may explore how to balance IL-6 activity to enhance protective immunity without causing harmful inflammation. Understanding the precise mechanisms of IL-6 in different infections could lead to improved flu treatments and vaccine strategies.
The study findings were published in the peer-reviewed journal: Mucosal Immunology.
https://www.sciencedirect.com/science/article/pii/S1933021925000194
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