COVID-19

Odds are that by now you’ve probably heard about the coronavirus. As suggested by the name, it is a virus- one that had been around for a really long time before now. However, it is believed to have recently mutated, giving it the ability to infect a new host: humans. COVID-19, like any other virus, is an obligate intracellular pathogen. This means that in order for the virus to replicate and spread, it must invade host cells. Fortunately, the human body has developed amazing ways of fighting off such diseases. Unfortunately, because our bodies have never seen a disease quite like this before, some people are unable to mount the immune response necessary to prevent life-threatening, and sometimes fatal, illness. There are a few different reasons why some people cannot fight off this illness as effectively as others. Patients who might be at a greater risk of serious illness from the coronavirus include the immunocompromised, those with preexisting conditions or those who were already sick, and those whose genes do not allow for the production of effective immune cell machinery. As you can see, the immune system plays a huge role in fighting off the coronavirus and infections in general. In the next couple paragraphs I’ll talk about how antibodies specifically interact with the coronavirus.

Antibodies and their interactions with COVID-19 antigens have been an essential part of testing for the sickness. As we have been studying, our bodies make millions of B cells with unique B cell receptors that are specific for a certain antigen. Once the B cell encounters this antigen within the body, with the correct signaling from a helper T cell, the B cell will become activated and produce millions and millions of copies of plasma cells, which will produce antibodies, and memory cells, which will help our bodies fight off the infection if we ever see it again. Because of the ways antibodies interact with antigens, doctors and scientists have been able to use our own antibody responses to the virus to determine whether or not we have been exposed to the virus. This is done by testing for antibodies that fight the coronavirus in our bloodstreams. As was mentioned before, antibodies will only be mass-produced after the virus is introduced into the body. Therefore, the presence of antibodies indicates that the patient either has the virus or had it previously and fought it off. These antibodies have been shown to provide resistance to future illness caused by the coronavirus in studies done in monkeys. This means that, according to this specific study, the antibodies those who are infected with the coronavirus make will protect them if they ever have to fight the illness again. Another interesting way of testing if someone has the coronavirus is taking a sample of the microbes in their upper respiratory secretions and applying it to special pieces of paper loaded with antibodies to the coronavirus. Then, some form of visual indicator will indicate whether or not the secretions contained coronavirus antigens.

Like I’ve tried to make abundantly clear, the body has amazing ways of protecting itself, and this is undoubtedly reflected in its immune response. For example, the body produces multiple types of antibodies. The relative concentration of antibodies can be measured in your blood with the use of titers. Titers can test for a couple different types of antibodies including IgM and IgG. IgM antibodies are the preliminary antibodies, the first ones your body produces in response to an infection. Although these antibodies are not particularly specific and do not fight off pathogens quite as efficiently as IgG antibodies do, they are a step in the right direction and an important first step in initiating the body’s defenses. Later on, as the immune response progresses, the immune cells produce IgG antibodies, which are “fine tuned” to fight off the specific infection at hand. It is present in the fluids of the body and will therefore be found in one’s blood. Someone with IgM antibody titers would be early on in their infection. As was said before, they have not yet begun producing specific antibodies to fight off this specific illness. However, someone with IgM and IgG antibody titers would indicate that they are actively fighting off the virus and that their adaptive immune system is actively working against the coronavirus specifically. Effector cells are doing their job fighting off the infection. If someone has an IgG antibody titer only, it indicates that the person has effectively fought off the infection and can no longer suffer from the same illness. The presence of IgG antibodies is exciting because it is a potential treatment for those who are suffering from the sickness now. These antibodies could be introduced to the bloodstream of someone fighting the coronavirus, giving them passive immunity and allowing them to get over the illness more quickly.