How Does the Immune System Fight Viruses and Infections?


Your immune system is your body’s best friend. It works around the clock to ensure you are protected from viruses and bacteria. Without a properly functioning immune system, you can be prone to more viruses or your immune system may be hyper-active, fighting off foreign invaders when it shouldn’t. In this article, we will go over what the immune system does, how it reacts to viruses, how it fights off an infection, and whether or not your immune system grows stronger after a cold. 

How Does Your Body Fight Off Viruses?

Your immune system works around the clock to fight off potentially harmful viruses and foreign invaders, taking action to eliminate them. When your immune system detects something that may be harmful, it releases chemicals that trigger virus-fighting cells. Believe it or not, many of the side effects of illnesses are signs that our body is working hard to fight off viruses, infections, or pathogens. Here are some signs that your body is fighting off a virus:

  • Runny nose - A runny nose helps wash germs from the nose and sinuses
  • Coughing and sneezing - Mucus is designed to trap viruses which are then expelled from the body through coughing and sneezing
  • Fever - Fevers work hard to fight influenza viruses. This is because viruses are sensitive to temperature changes and cannot survive above body heat
  • Muscle aches and pain - You may experience sore muscles with the flu as it is also a product of your body’s immune response. The immune system pulls protein from muscles, leaving your muscles achy

As you can see, many of the signs of illness are actually signs that your immune system is working to protect your body. 

How Does a Virus Leave the Body?

A virus invades our body in order to survive and replicate. Once inside the body, the cells of our immune systems struggle to see the virus and are unable to tell that the host cell is infected. To combat this, cells employ a system that allows them to show other cells what is inside of them. They use a molecule known as the MHC class I molecule. This molecule works to display pieces of protein from inside the cell upon the cell surface. 

A special cell of the immune system called a T cell circulates looking for infections. If the T cell receptor detects a peptide from a virus, it warns its T cell of an infection. The T cell releases cytotoxic factors to kill the infected cell and, therefore, prevent the survival of the invading virus. 

Unfortunately, viruses can be very “smart” and most have evolved to avoid detection by T cells. If this happens, another immune cell designed to kill cells that have a reduced number of MHC class I molecules on their surface is the NK cell. When the NK cell finds a cell displaying fewer than normal MHC molecules it releases toxic substances, in a similar way to cytotoxic (sai-tow-taak-suhk) T cells, which kill the virally-infected cell.

How Does the Immune System Cause Fever?

When the immune system detects a virus or bacteria, it produces chemicals called pyrogens (pai-row-jnz). These pyrogens trick the brain’s hypothalamus (hai-puh-tha-luh-muhs) into sensing an artificially cool body temperature. In response to this, the brain responds by kicking up the temperature a few notches. 

Blood then rushes to the body’s core, heating the body overall but cooling the surface - which is why you feel chills when you have a fever. The body's metabolic rate goes up and muscles contract. Viruses and bacteria can only live at normal body temperature, so kicking up the heat oftentimes kills off the virus. 

How Does Your Immune System Fight Infection?

Germs can find their way into your skin in a number of different ways. More often than not, they find their way in through an open wound - most likely a cut. But they can also find their way in through your eyes and mouth. This is why it’s incredibly important to regularly wash your wands to keep bacteria off them! 

When bacteria make their way into your body and lead to an infection your white blood cells get hard to work. White blood cells are made in your bone marrow and they have a short life - often only living a few days, maybe even a few weeks - so your body can constantly make more. There are different types of white blood cells but they all work to fight off infection. 

Is Your Immune System Stronger After a Cold?

One of the major strengths of your immune system is that it remembers the viruses and bacteria it fought off. On top of that, antibodies of the virus remain in your body long after the infection has resolved. This means your body will make more of them if you are exposed to the same virus again. This will provide a faster response and possibly prevent the infection from occurring again. 

So yes, in theory, your immune system is stronger after a cold. However, there are an estimated 200 different cold viruses, and you will rarely face the same one twice. While you might indeed now be able to thwart re-infection with a virus you've already had, there is likely to be another in your future for which your body hasn't yet had a chance to develop an antibody defense.

Is Getting a Cold Good for Your Immune System?

As we just mentioned, your immune system can become more efficient at fighting off viruses after already dealing with them once. In this way, getting a cold is good for your immune system. Your body fighting off a cold is also a good sign that your immune system is working as it should, fighting off foreign invaders. 

However, that doesn’t mean that you should be going around actively looking to catch a cold in order to boost your immune system. The best way to strengthen your immune system is by living a healthy lifestyle. An unhealthy lifestyle can lead to a hyperactive immune system, which can cause long term issues. 

Supplements Can Help

There are several processes our body uses to remove antigens. One of the protective systems involves our bodies producing macrophages (ma-krow-fei-jiz), those macrophages engulf the antigen, and then the antigen is digested (destroyed) through a process of autophagy. Early studies show that spermidine triggers cellular autophagy, which can play a major role in helping to build a more robust immune defense through healthier cells and increased autophagic strength and function.

The positive impacts of spermidine-induced autophagy and spermidine supplementation have been studied worldwide. In addition to boosting our immune system, spermidineLIFE offers remarkable supplemental support for the health of our brain, heart, bones, muscles, weight, hair, liver, and overall longevity.

  • Don Moxley - Director of Applied Science

    Don Moxley is the Director of Applied Science at Longevity Labs. Moxley draws upon his career as an athlete, a sports scientist, and an instructor to lead and educate on the science of autophagy and longevity.