You’re hopefully not going to die of the flu this year. But the truth is that you could.
Once the virus that causes the flu enters the body, it begins to multiply and cause damage to the respiratory system (nose, throat, and lungs). Children, pregnant women, adults over 65, and patients with compromised or weakened immune systems are all at risk of developing secondary complications from the flu, as damage done to the body by the flu virus can lead to increased risk of additional illness, and in severe cases death. Infectious agents, and others that cause damage to cells, are referred to as pathogens. Viruses are one of five classes of pathogens, along with bacteria, protozoa, fungi, and prions. It can be hard to believe that a pathogen isn’t innately bad when it’s causing physical discomfort and damage to your body, but pathogens are simply doing what living things do—looking for a nutrient-rich environment that will allow them to survive and reproduce. The human body is the home some of these pathogens like best.
The word “immune” can be traced back to Latin and French roots meaning exempt from and privileged from attack. The immune system, and the protection it confers, offers exactly that. There are two branches of the immune system: innate immunity, comprising nonspecific responses, and adaptive immunity, which can learn to recognize and respond to a specific pathogen. Upon infection, these two branches work in conjunction with one another to clear pathogens. Overall there are three lines of defense, the first two by the innate response, and the third by the adaptive response.
But pathogens do often gain entry, and a main component of our immune system’s ability to clear harmful microorganisms comes from the ability to discern between self and nonself. The immune system can recognize cells, proteins, and other molecules that our body has made as “self,” and it also can recognize foreign proteins, particles, DNA, toxins, and chemicals from pathogens as “nonself” and can then target and induce an immune response against them. In Chicago, a city of 2.7 million, we don’t all agree on what’s harmful or nonself, but crimes, car accidents, and mass shootings are things we all recognize as harmful. Sometimes the body loses the ability to discern between self and nonself, which results in autoimmune diseases: the body attacks itself instead of protecting it. Similarly, the Chicago Police Department is supposed to serve and keep the residents of the city safe, but improper police training and consistent lack of accountability around conduct have resulted in repeated violations of justice and abuse through illegal searches, excessive force, and racial profiling and biases, leading to harm and even death of the city’s residents.
Previously, it’s been thought that children are more susceptible to the flu and other viral infections because they are not yet able to mount the thorough innate immune response that healthy adults are capable of. A paper published in April by researchers at Lurie Children’s Hospital and Northwestern University’s Feinberg School of Medicine reported findings that overwhelming inflammatory and monocyte responses were responsible for increased lung damage in juvenile mice infected with the flu in comparison to adult mice. These components of the innate immune system help fight infection, but they also cause a lot of the symptoms experienced during infection and sometimes the response harms the body.
Once activated, T cells send signals that call for backup: the body clones many identical T cells that are made to specifically recognize, target, and destroy that unique antigen. This process can be compared to using X-rays and laboratory tests to confirm the presence of a malignant tumor, and the establishment of a multidisciplinary cancer team to collectively plan the best course of action, for example, surgery followed by chemotherapy. These T cells have been given the description of the pathogen and are only able to bind to antigens or pathogens whose fingerprint is an exact match for the one they’re trying to find. This process is called cell-mediated immunity. Separately, that same signal that gets sent out by the T cell once it’s activated stimulates and activates B cells to respond if they haven’t already been activated by directly encountering the pathogen. B cells can be considered another component of the T-cell/cancer treatment team. In addition to the doctors and specialized care team, a supportive care team composed of counselors, nutritionists, and rehabilitation therapists works with patients to support long-term health. Activation of B cells results in the production of clone B cells, called plasma cells, that produce antibodies that will specifically bind to the antigen of the encountered pathogen and clear them from the body. Analogously, your therapist may recognize certain patterns they guide you to focus on to help you respond to them in a different way so that those issues no longer affect you. It takes a few days for this response to occur, which is why the innate immune system’s quicker initial response is so important. Additionally, after the infection has cleared, some of these activated B cells remain in circulation. If they encounter the antigen again in the future, the circulating B cells can produce antibodies and a specific response in one to two days. If you get emotionally triggered, you draw on the skills learned in therapy or reach back out to your therapist to get more help, and over time your capacity to handle hard issues increases as you heal. Similarly, the adaptive immune response and its encounter with pathogens leads to memory and immune protection.
