Gracia Lam / Courtesy of the New York Times

September 21, 2020

A Look Into The Immune System: Cornell Experts Explain How Our Bodies Fight Disease

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In the middle of a global pandemic, people now, more than ever, are invested in understanding how their immune system works.

Although many questions remain in the field of immunology research, The Sun interviewed three Cornell researchers to understand how the immune system functions when faced with an illness, and what experts recommend doing to assist the immune system in fighting off illness.

The immune system is always on the lookout for pathogens

Pathogens can enter the body in multiple ways, according to Prof. Cynthia Leifer, microbiology and immunology. These include the mouth and nose through either breathing in the pathogen or by touching your mouth, nose or eyes. Pathogens can also spread through eating something that contains pathogens or getting bit by a disease-carrying insect.

Whichever way pathogens enter the body, they will try to begin multiplying. According to Leifer, some bacteria can divide on their own, while viruses must hijack cells from the organism in order to reproduce.

“Your body has basically a little army of cells that are constantly looking around for pathogens, and they have these little molecules on their surface called proteins that recognize the infectious agent,” Leifer said.

The immune response has multiple components 

Once a pathogen is detected, the first response is non-specific, focusing on limiting pathogen spread in ways that would impact any infectious agent rather than a specific bacteria, virus or other infectious agent.

“There are events that happen very early on, and we call those innate mechanisms,” Leifer wrote in a follow-up email. “Those are just very rapid responses against an invading pathogen coming in, and these responses are relatively nonspecific.”

According to lecturer Beth Rhoades, microbiology and immunology, the immune system includes T cells, which identify and kill infected cells, and macrophages, which dispose of the debris. There is also an adaptive response, which is largely driven by T cells and B cells — cells that produce antibodies.

“Antibodies are molecules that will tag a pathogen and say, eliminate this pathogen whatever is tagged with an antibody is in trouble,” Rhoades said. “The rest of the immune system will pick it up and destroy it one way or the other.”

If the immune system has seen a pathogen before, it is better prepared to respond, according to Rhoades. Once B and T cells recognize a pathogen, they duplicate themselves, making what Leifer called a “clonal army in order to fight that infection.”

This memory response can be developed either by having the illness before, or through vaccination, which, unlike getting infected, is a safe way of developing a memory immune response.

“It is often better to get a vaccine than to have a natural infection with a pathogen since vaccines are very safe and very effective,” Leifer wrote.

Some pathogens can’t stand the heat, but neither can people

A commonly misunderstood part of the immune system is fevers, a substantial rise in body temperature, which the immune system creates to fight off an illness.

“The problem is that when you’re talking about viruses, you’re talking about millions and millions of them,” said Prof. Hector Aguilar-Carreno, microbiology and immunology. “When you raise the temperature, you’re going to kill some of them, but not all of them.”

According to Aguilar-Carreno, if a small number of viruses survive dehydration at high temperatures, these viruses can continue to reproduce. For this reason, while the fever response can help promote recovery, high temperatures alone do not guarantee that illnesses won’t spread in or outside the body.

Fevers can not only dehydrate the pathogens infecting someone, but also the person. For this reason, medical professionals often work to alleviate the fever component of the immune response.

Too little of an immune response is bad, but so is too much 

While too little of an immune response risks letting an infection progress, damaging tissues and endangering someone’s life, too strong of an immune response can also have repercussions. An overactive immune response can cause inflammation and tissue damage, according to Leifer.

“You want the Goldilocks zone, where you have just the right immune response to kill the pathogen and not damage your own tissues,” Leifer said.

COVID-19 exemplifies the need for staying within this zone as both the virus itself and the immune system response to it pose a risk. While the coronavirus is a threat, so is the inflammatory response it can provoke in the lungs and other organs, causing tissue damage, according to Leifer.

Strengthening the overall immune response is a complex task

While vaccines are well established as a safe way to develop immunity to specific pathogens, scientists are still working on finding out how to strengthen the immune system as a whole, and trying to understand what gives someone a stronger or weaker immune system.

According to Aguilar-Carreno, while researchers have determined that a balanced diet and exercise contributes to a healthy immune system, they are still working on determining mechanisms for why this is the case.

While many people may think that vitamin C and other supplements strengthen their immune system, Rhoades cautions against thinking that any one approach can make a perfect immune system.

“There are all sorts of supplements that contribute to having a healthy immune system, but there’s no magic bullet,” Rhoades wrote in a follow-up email. “The best thing that you can do is to get vaccinated, if you are able, and allow your body to set in place all of the layers of the immune response that you need.”