What are T cells? Let's learn more about our body's defenses!

Have you ever thought that we have a small but very powerful army inside our bodies to fight diseases? T cells are a special part of this army that protects us from enemies like viruses and bacteria without us knowing. These are really like little heroes in our bodies. Today, let's talk about these little heroes in a simple way.

What exactly are T cells?

Simply put, T cells are a type of white blood cell in our blood. In medical terms, they are called lymphocytes. These cells, called lymphocytes, play a very important role in our immune system . The immune system is the defense system that fights germs, such as viruses, bacteria, and fungi, that enter our body. Not only that, this system also works to destroy things that are harmful to the body, such as cancer cells.

There are two main types of soldiers in our lymphocyte army. They are T cells and B cells . Together, they protect us.

• B cells: These cells make special proteins called antibodies. These antibodies go and destroy pathogens.
• T cells: These work a little differently. T cells go straight to our own cells that have been infected with germs and destroy things like cancer cells. They also send signals to other cells in the immune system, telling them, "This is how we should fight."

Are there main types of T cells?

Yes, there are two main groups of T cells. Just like an army has an attack force and a commanding officer. Let's see who they are.

In addition to these two main types, there are also regulatory T cells . Their job is to control the activity of other T cells when the fight is over or when needed. This is very important, because otherwise our T cells could attack our own healthy cells.

How do these T cells work?

T cells are part of the adaptive immune system. Think of them as a highly advanced "smart defense system." They are constantly on the lookout for enemies. Once they recognize an enemy, they mount a specific attack against that enemy.

When the immune system recognizes an enemy, it finds the specific T cell that can destroy that enemy and calls it into action. That T cell then makes thousands of copies of itself. The T cells that join this fight are called effector cells . These effector cells are what destroy the enemy and protect us from disease.

T cells protect us even after the fight is over. Some T cells, instead of becoming trigger cells, become memory cells . These memory cells don't fight. Instead, they remember the details of the enemy. If the same enemy ever comes back to the body, these memory cells allow the immune system to quickly recognize it and launch an attack with the same old plan.

How does a T cell get ready for battle (activated)?

A T cell doesn't just go and fight. It has to be activated first. There are several steps to that.

1. First, a special cell called an antigen-presenting cell (APC) finds evidence of the enemy (for example, a piece of a virus) and attaches it to a structure called the major histocompatibility complex (MHC) . This is like taking a police photo of a thief and putting it on a billboard. T cells cannot recognize the enemy directly, they can only recognize it when it is presented on this MHC.

2. Next, the T cell comes in and binds to this MHC. But not every T cell can bind to every MHC. Killer T cells (CD8+) can only bind to type I MHC. Helper T cells (CD4+) can only bind to type II MHC. It's like a match for a key and a lock.

3. When everything is aligned in this way, the T cell is activated. That's when it goes into battle. This alignment is very important, because it ensures that the right T cell for that enemy goes into battle.

Where are T cells produced and located in our body?

The life cycle of T cells is like a little journey. At different stages of that journey, they are in different places.

• Birthplace - Bone marrow: The soft tissue inside our bones, called bone marrow, is where T cells first develop. Like all blood cells, T cells start out as hematopoietic stem cells .
• Training School - Thymus: These immature T cells (called thymocytes) then travel to the thymus, an organ in the upper middle of our chest, to be trained. The thymus is like the "military training school" for T cells. Here, they are tested to see if they can properly bind to MHC and not attack our own healthy cells. This is also where they receive their "identity card" - CD4 or CD8. Only T cells that pass all these tests are released.
• Fields of Duty - Lymphatic Tissue and Blood: Well-trained T cells then travel to our lymph system, such as the spleen, tonsils, and lymph nodes. Some also circulate in the blood. It is here that they sit, waiting for a call to action.

What diseases and conditions affect T cells?

There are several types of diseases that affect the function of T cells. These can be mainly classified as autoimmune diseases and immunodeficiency disorders . In autoimmune diseases, the immune system mistakenly attacks our own healthy cells. Immunodeficiency diseases are conditions in which the immune system is weakened.

Some conditions that can affect T cells include:

• Acute lymphocytic leukemia: A type of cancer that begins in the blood and bone marrow.
• Adult Hodgkin lymphoma: A type of blood cancer that begins in the lymphatic system.
• T-cell lymphomas: Cancers that begin in T cells.
• HIV (Human Immunodeficiency Virus): This virus mainly attacks our helper T cells (CD4+ T cells). This can lead to the breakdown of the command center of the immune system, leading to AIDS.
• DiGeorge syndrome: A genetic condition that prevents the body from producing enough healthy T cells.
• Severe combined immunodeficiency (SCID): A group of rare genetic diseases in which the immune system is very weak due to problems with T cells.

What should be the normal number of T cells?

The normal range of T cells in a healthy adult is:

• CD4 (helper T cells) count: Between 500 - 1,200 cells per cubic millimeter.
• CD8 (killer T cells) count: Between 150 - 1,000 cells per cubic millimeter.

However, these values ​​may vary slightly depending on the lab that performs your blood test. Therefore , it is best to talk to your doctor to get the most accurate information about the values ​​in your report.

What does it mean to have a decrease in T cells?

A low T cell count means that the immune system is weak. This means that you are more susceptible to germs. There can be several reasons for a low T cell count. For example, genetic diseases that are present at birth, diseases that are acquired later, such as HIV, or certain medications (such as cancer treatments) can also cause a low T cell count.

What does it mean to increase T cells?

An overproduction of T cells is rare. It usually occurs when the immune system produces too many T cells to fight an infection in the body. Some types of cancer can also cause an increase in T cells.

How can we increase the strength of our T cells?

There are specific medications or treatments that can help boost T-cells, but they should only be taken under medical supervision. Talk to your doctor about them. But there are also many things we can do to keep our immune systems strong in general. Sometimes the best way to protect our T-cells is to not overwork them. That means staying away from germs as much as possible and taking good care of your body.

• Eat a good, balanced diet .
• Get all your vaccinations on time.
• Avoid alcohol and smoking completely.
• Get at least 7-8 hours of good sleep every night.
• Engage in at least 150 minutes of moderate exercise per week.
• Wash your hands with soap as thoroughly as possible.

T cells, immune system, white blood cells, lymphocytes, CD4, CD8, HIV, cancer