Our First Line Of Defense: Immune System | Healthystripe
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Our First Line of Defense: Immune System

HealthyStripe's Editorial Team
18 September 2021

We live in a world that is fully surrounded by microorganisms that could harm our health in some way or the other. Be it railing of the metro station, buttons in the lift, or even when you purchase your favourite delicacies from the market. Every item can have some microbes attached to it that may get unnoticed.

If this is the case, then how come we are so fit and fine in this microbial world? 

Well! Immunity always has the upper hand in protecting us against these threats for our survival. It acts as the first line of defense against any threat to our body.

How does the Immune system respond to these threats?

The immune system on our body is a complex network that comprises particular immune cells and proteins which protect our body from all the foreign invaders and harmful viruses coming in contact with us.

Foreign substances that help to activate an immune response are called antigens. However,at times, such as in autoimmune diseases, the immune system can be activated by self-antigens, leading to the destruction of the body’s cellular components.

For instance, the immune system can be activated to generate two types of immune responses: nonspecific response (innate immunity) and specific adaptive response (acquired immunity).

What are the three lines of defense in the immune system?

Before going into a deep understanding of this, let me tell you that our immune system consists of three levels of defense mechanisms that pathogens have to cross to develop infections inside the human body.

What is the body’s first line of defense against pathogens?


Physical barriers are the skin and mucosa of the digestive and respiratory tracts which help to eliminate pathogens and prevent tissue and blood infections. 

Moreover, components that are secreted by the skin or mucosa, such as sweat, saliva, tears, and mucous help us provide a strong barrier against invading pathogens.

The skin is the impermeable barrier that protects many pathogens from entering the body. Likewise, mucous membranes that line the immediate internal systems help trap pathogens by producing mucus. Hairs inside the nasal cavity, as well as cerumen (earwax), also trap pathogens and environmental pollutants effectively.

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Some examples of the first line of defense are:

Certain acidic fluids in the body like gastric juice, urine, and vaginal secretions, destroy pathogens by creating low pH conditions. Also, lysozyme found in tears, sweat, and saliva acts as a vital antimicrobial agent that can kill pathogens and acts as an effective first line defense against the pathogens. 

What is the body’s second line of defense against pathogens?


The second line of defense is a group of cells, tissues, and organs that work collectively to protect your body. 

When a pathogen invades the human body, the neutrophils gather at the entry site and try to engulf it and destroy it. The macrophages (big eaters) will be attracted by the death throes of the neutrophils. These cells attempt to engulf the invader, but they also alarm other cells for help.

If the invading organism is a virus then the T helper cell will signal the cytotoxic (killer) T cells to come to the rescue. If the invader is a bacteria, B cells come to the rescue. They put an antibody (IgG) onto the bacteria. This sticks everything together and makes it attractive to macrophages, which clears up all the mess.

Very often, this line of defense is enough to resolve the infection. At the very least, it can limit the spread of infection. For example, the bacteria that entered through the cut on your leg might not spread any further into your body.

But there are some situations where the innate immune system is not enough to fight off. For example, there might be too many bacteria, or the bacteria might multiply too quickly. That’s when your adaptive immune response will do it’s work!

What is the body’s third line of defense against pathogens?


The third level of defense consists of cells tailor-made to get rid of the specific microorganisms that have invaded your tissue.

Special cells called dendritic cells are the point of communication between innate and adaptive immunity. 

Macrophages, along with dendritic cells, travel to the site of infection, where they phagocytose and break off small parts of the pathogen. They carry these parts to your lymph nodes, where adaptive immunity begins. 

The adaptive immune response has two main types of specialized white blood cells called lymphocytes – B cells and T cells. B cells are found in the blood. Their main function is to mature into cells that produce antibodies to fend off foreign invaders that get into the body. To do this, they work along with the T cells. 

Eventually, T cells will eliminate the infection just after the days it has been activated. At this point, your body can stop fighting by sending a ‘calm down’ signal to your immune function, and you will start to feel better.

Why is the first line of defense important for you?

The first line of defense is the primary surface barrier against the entry of the pathogens. These surface barriers include intact skin which protect the external boundaries and mucous membranes which protect the internal boundaries. 

Both the skin and mucous membranes release chemical secretions which prevent the growth of microbes on their surfaces. Just think that if pathogens cannot enter the host body then they cannot disrupt the normal physiological functions of the body and cause any harm to your body. [Fact Source]

Now, How can you boost your immune system?

Here, we have jotted down some easy ways to boost your immune health in a hale and hearty way:

  • Eat plenty of fresh fruits & vegetables.
  • Inculcate a habit of regular exercise.
  • Make yourself a cup of immunity-boosting tea filled with natural herbs.
  • Go for antioxidant-rich foods and try adding them to your diet through healthy smoothies to make things interesting with a twist of taste.
  • Don’t forget to get a good amount of sleep!


The immune system is a network of cells, tissues, and organs that help the body fight off infection from outsider invaders, like bacteria, virus, fungi, and toxins. It’s a highly complex biological system that requires a balance between all parts to function properly. 

This means optimal immune health relies on a multifaceted approach that puts a major focus on making healthy lifestyle choices. 

Also, it will do wonders if we make a barrier for these foreign invaders at the first line of defense of our body- skin and mucous membranes by being extra cautious of our health. 

So, next time you get a small cut or forget to wash your hands, take extra care. After all, prevention is better than cure!

Also Checkout: Best Teas For Immune System | Herbs To Boost Immune System | Best Antioxidant Drinks

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