Scientists uncover impact of infections on immune system
Our immune system is critical in the battle against outside invaders such as viruses, parasites and bacteria that can cause infections. If a pathogen is successful in evading our initial defences, then our bodies will try to fight the infection until we are healthy again. “Specific pathogens have been studied intensively, in order to better understand what they do to our bodies and how our immune systems respond when they try to fight them,” explains Immune Regulation project coordinator Nicole Joller from the University of Zurich in Switzerland. “This work has been tremendously important in the development of vaccines, which, as we’ve seen most recently with coronavirus (COVID-19), can save lives.”
Immune system and pathogens
One area of focus that has received less attention however has been the long-term impact of interactions between our immune system and pathogens. We still don’t fully understand how the immune response to one pathogen alters the body’s ability to respond to a second infectious agent or affects our susceptibility to autoimmunity or cancer. To examine this question, Joller sought to take a more holistic view of the influence of pathogens on the immune system. The Immune Regulation project, funded by the European Research Council, focused on learning more about how ‘brakes’ in the immune system – which are called regulatory T-cells or ‘Tregs’ – are applied, and what wider consequences this might have. “The immune response comes in different flavours, to combat different types of viruses, bacteria or parasites,” adds Joller. “If you catch a virus, then your body will typically not only push the best suited response to fight the virus but also hit the ‘brakes’ to stop the wrong kind of immune response, i.e. a response to fungi or bacteria, from happening.” This is critically important, because an overactive immune response will lead to the body attacking healthy cells and tissues.
Holistic view of disease
The Immune Regulation project enabled Joller and her team to investigate in mouse models how immune systems are affected in real time. This has led to some interesting discoveries. “We have seen that it is OK if these ‘brakes’ don’t work for a period of time, as this allows the ‘drivers’ to kick-start the fight against the pathogen,” says Joller. “But we also found that such delays could be the first seed in the development of autoimmune disease.” Similar findings were made and emphasise the benefits of taking a more holistic view to pathogens. “Colitis is not caused by viral infection for example,” notes Joller. “But we have seen that viral infections can sow the seeds for this disease.” In other words, a war between a pathogen and the immune system that gets out of control can leave behind a lot of damage, leaving the host organism potentially more susceptible to other types of diseases such as autoimmunity.
Potential new therapies
Achieving a better understanding of how the immune system is regulated could one day lead to possible new therapies for treating autoimmune diseases, as well as cancer. Being able to introduce more focused ‘brakes’ that target specific pathogens could be a more effective means of treatment, with fewer side effects. “For example, the respiratory syncytial virus, which infects lots of children every year, can lead to lung damage induced by the immune system,” says Joller. “If we could find a way of dampening the immune response, then we might be able to help children avoid developing asthma in later life.”
Keywords
Immune Regulation, autoimmune, viruses, bacterial, diseases, infection, pathogen
