Here's How Our Body Responds to Viral Infections

Have you ever been curious about how immunity develops? It's a straightforward process that can be fascinating to explore.

People infected with the coronavirus often experience a wide array of symptoms. This variability continues to puzzle scientists and medical professionals. Some individuals show no symptoms at all, while others may experience mild to severe reactions, such as fluid buildup in the lungs or blood clots, which can be fatal.

Currently, there are no vaccines or proven treatments available, leaving supportive care and a few repurposed medications as the primary options. Research indicates that our immune system plays a crucial role in recovery from COVID-19.

What happens when a virus invades our body? Let's explore the incredible immune response.

The Body's Remarkable Defense System

Our immune system is made up of millions of white blood cells known as leukocytes, which are constantly on the lookout for threats. Some of these cells travel through the bloodstream, while others reside in tissues to combat infections. As they navigate through the body, leukocytes act as vigilant guards, scanning for anything that appears suspicious.

Since threats can vary widely, leukocytes have adapted to tackle different types of invading microorganisms. They can be divided into two primary categories: phagocytes and lymphocytes.

Phagocytes, which literally means "cell eaters" in Greek, destroy invaders by engulfing them. They provide an innate form of immunity. Conversely, lymphocytes adapt their attack strategies to target specific pathogens, offering a form of adaptive immunity.

Phagocytes and lymphocytes work together in a coordinated effort to eliminate viruses.

In the video "MEDventure: Immune system – How does our body defend itself against pathogens?", viewers can learn more about the intricate workings of our immune response and how it protects us from various pathogens.

The Structure of a Virus

Viruses have a simple structure composed of DNA or RNA encased in a protective layer. They cannot survive independently; instead, they invade host cells, hijack their machinery, and replicate themselves.

While our immune system is adept at combating many infections, it struggles against viruses since they can hide inside host cells. Once a virus multiplies, the infected cell either bursts or gradually releases new viruses, continuing the cycle of infection.

Fortunately, as viruses replicate, they produce unique molecules known as antigens that serve as markers on infected cells, allowing the immune system to differentiate between "self" and "non-self."

Interferons, another important defense mechanism, are released by infected cells to alert neighboring cells to enhance their defenses against viral replication.

The Role of White Blood Cells

When phagocytes detect foreign antigens, the immune response is initiated within minutes. This triggers a well-coordinated series of actions to combat the virus.

Phagocytes first consume infected cells and then release cytokines, which inform lymphocytes about the nature of the viral threat, causing inflammation in the process.

Upon receiving this information, T cells, a type of lymphocyte, seek out and destroy infected cells. Meanwhile, B cells produce antibodies—specialized proteins that target specific antigens.

Visual representation of antibody (Y-shaped) and virus. Illustration Credit: Peter Schreiber / Shutterstock. Source: NewsMedical Lifesciences

Each antibody is tailored to a unique antigen, akin to a lock and key. When an antibody binds to its corresponding antigen on an infected cell, it sets off a chain reaction that leads to the cell's destruction. This is how antibodies contribute to our immune resistance.

During this battle, our bodies may exhibit familiar symptoms such as fever, runny nose, and cough, which serve several purposes. They alert the body of an ongoing fight, help expel the virus, and guide white blood cells to the infection site.

The symptoms can vary based on where the virus settles in the body. For instance, a respiratory virus may cause coughing, while a gastrointestinal virus might lead to diarrhea.

The Immune System’s Response to COVID-19

While our immune system is capable of tackling many infections, the coronavirus poses unique challenges. Most deaths related to COVID-19 do not result directly from the virus but rather from the immune response going into overdrive.

In cases of mild attacks, the immune system typically manages to eliminate the virus effectively. However, in some instances, it can overreact, producing excessive inflammatory molecules that can lead to severe symptoms, such as pneumonia.

Additionally, viruses can adapt and develop mechanisms to evade the immune system. For example, the D614G mutation in the coronavirus allows it to more effectively enter host cells, increasing its contagiousness.

People with weakened immune systems, such as the elderly or those with pre-existing conditions, are particularly vulnerable to severe outcomes from viral infections.

Supporting Our Immune Health

These are challenging times, and the uncertainty surrounding COVID-19 can lead to anxiety. However, we can take proactive steps to support our immune systems.

Maintaining a healthy lifestyle is crucial. Prioritize regular sleep, exercise, and a diet rich in fruits, vegetables, and well-cooked meats.

As the saying goes, "Prevention is better than cure." Until a reliable vaccine is available, our best defense is to avoid exposure to the virus through social distancing, wearing masks, and practicing good hand hygiene.

By educating ourselves and supporting one another, we can contribute to the fight against COVID-19.