The immune system normally stays dormant within the lungs in occasions of well being. Overactive immune system may cause points like bronchial asthma and allergy symptoms, making it exhausting to breathe.
Lengthy COVID-19 and other chronic respiratory conditions after viral infections may stem from an overactive immune response in the lungs.
Shortly after the beginning of the COVID-19 pandemic, anecdotal reports emerged of previously healthy individuals that were experiencing lingering symptoms and were not fully recovering from an infection with SARS-CoV-2. These patients started to refer to themselves as “Long Haulers,” and they coined the term “Long COVID.”
Viruses that cause respiratory diseases such as the flu and COVID-19 can lead to mild to severe symptoms within the first few weeks of infection. Usually, these symptoms resolve on their own within a few more weeks. Sometimes, if the infection is severe, treatments are needed to aid recovery. However, some people go on to experience persistent symptoms that last several months to years. It is still unclear why and how respiratory diseases can develop into chronic conditions like long COVID-19.
I am a doctoral student working in the Sun Lab at the University of Virginia. We study how the immune system sometimes goes awry after fighting off viral infections. We also develop ways to target the immune system to prevent further complications without weakening its ability to protect against future infections. Our recently published review of the research in this area found that it is becoming clearer that long COVID-19 and similar conditions might not be caused by an active viral infection. Instead, they are caused by an overactive immune system.
Lengthy COVID-19 sufferers can expertise persistent respiratory, cognitive, and neurological signs.
The lungs in well being and illness
In your lungs to have the ability to operate optimally, it’s important that your immune system stay dormant when there isn’t an energetic an infection.
Individuals name post-COVID situations by many names, together with: lengthy COVID, continual COVID, post-acute COVID-19, long-term results of COVID, post-acute sequelae of SARS CoV-2 an infection (PASC), and long-haul COVID.
Your respiratory tract is in fixed contact together with your exterior atmosphere, sampling round 5 to 8 liters (1.3 to 2 gallons) of air – and the toxins and microorganisms in it – each minute. Regardless of steady publicity to potential pathogens and dangerous substances, your physique has developed to keep the immune system dormant in the lungs. In actual fact, allergy symptoms and situations similar to bronchial asthma are byproducts of an overactive immune system. These extreme immune responses may cause your airways to constrict and make it troublesome to breathe. Some extreme instances might require therapy to suppress the immune system.
Throughout an energetic an infection, nonetheless, the immune system is completely important. When viruses infect your respiratory tract, immune cells are recruited to your lungs to struggle off the an infection. Though these cells are essential to eliminating the virus out of your physique, their exercise typically ends in collateral harm to your lung tissue. After the virus is eliminated, your physique dampens your immune system to provide your lungs an opportunity to recuperate.
An overactive immune system, as within the case of bronchial asthma, can harm the lungs.
Over the previous decade, scientists have recognized a wide range of specialized stem cells in the lungs that may assist regenerate broken tissue. These stem cells can flip into nearly all of the several types of cells within the lungs relying on the alerts they obtain from their surrounding atmosphere. Recent studies have highlighted the outstanding position the immune system performs in offering alerts that facilitate lung restoration. However these alerts can produce a couple of impact. They cannot solely activate stem cells, but additionally perpetuate damaging inflammatory processes within the lung. Due to this fact, your physique tightly regulates when, the place and the way strongly these alerts are made with the intention to forestall additional harm.
Whereas the explanations are nonetheless unclear, some individuals are unable to show off their immune system after an infection and continue to produce tissue-damaging molecules long after the virus has been flushed out. This not solely additional damages the lungs, but additionally interferes with regeneration through the lung’s resident stem cells. This phenomenon may end up in continual illness, as seen in a number of respiratory viral infections together with COVID-19, Middle East Respiratory Syndrome (MERS), respiratory syncytial virus (RSV), and the common cold.
The immune system’s position in continual illness
In our assessment, my colleagues and I discovered that many different types of immune cells are concerned within the growth of continual illness after respiratory viral infections, together with lengthy COVID-19.
Researchers thus far have recognized one specific kind of immune cell, killer T cells, as potential contributors to continual illness. Also referred to as cytotoxic or CD8+ T cells, they concentrate on killing contaminated cells both by interacting straight with them or by producing damaging molecules known as cytokines.
Killer T cells are important to curbing the virus from spreading within the physique throughout an energetic an infection. However their persistence within the lungs after the an infection has resolved is linked to prolonged reduced respiratory function. Furthermore, animal research have proven that removing killer T cells from the lungs after an infection might enhance lung operate and tissue restore.
A legion of immune cells work collectively to take away invading pathogens.
One other kind of immune cell known as monocytes are additionally concerned in preventing respiratory infections, serving among the many first responders by producing virus- and tissue-damaging cytokines. Analysis has discovered that these cells additionally continue to accumulate within the lungs of lengthy COVID-19 sufferers and promote a pro-inflammatory atmosphere that may trigger additional harm.
Understanding the immunological mechanisms underlying lengthy COVID-19 is step one to addressing a quickly worsening public health problem. Figuring out the refined variations in how the identical immune cells that defend you throughout an energetic an infection can later turn into dangerous might result in earlier analysis of lengthy COVID-19. Furthermore, primarily based on our findings, my crew and I imagine therapies that concentrate on the immune system could possibly be an efficient method to handle lengthy COVID-19 signs. We imagine that this technique might grow to be helpful not just for COVID-19, but additionally for different respiratory viral infections that result in continual illness as effectively.
Written by Harish Narasimhan, PhD Candidate in Immunology, College of Virginia.
This text was first revealed in The Conversation.
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