LOL – Lots of Lymphocytes

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Ever wonder what is the essence of lymphocytes in our immune system and how does it affect our body? Here is the answer to your curiosity:

At some point in our lives, we all deal with sickness in one form or another. The manner in which we’re able to deal with sickness normally depends on the strength of our immune system. One of the main tools in the arsenal of our immune system is a group of specialized cells known as lymphocytes

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Lymphocytes are the second most common white blood cell (20-50%), and are easy to find in blood smears. Although the cells look similar there are two main types, B-cells and T-cells. But there is also called natural killer cells which is also considered as one of its type where they are known to be cytotoxic. This means that they have the ability to kill other cells. These cells are an important part of the immune system because they are able to recognize virally infected cells, as well as some types of tumor cells, and kill them before they cause a great amount of harm.

B-cells develop in the bone marrow. T cells are born in the bone marrow, but are matured in the Thymus. The B-cells develop into plasma cells which make antibodies, The T-cells attack viruses, cancer cells, and transplants.

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This is a photo of a lymphocyte in a blood smear. Most of the lymphocytes are small; a bit bigger than red blood cells, at about 6-9µm in diameter,

So what is the function of Lymphocytes in our immune system?

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T- and B-cells are highly specialized defender cells – different groups of cells are tailored to different germs. When your body is infected with a particular germ, only the T- and B-cells that recognize it will respond. These selected cells then quickly multiply, creating an army of identical cells to fight the infection. Special types of T- and B-cells ‘remember’ the invader, making you immune to a second attack.

 

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Having recognized the invader, different types of T-cell then have different jobs to do. Some send chemical instructions (cytokines) to the rest of the immune system. Your body can then produce the most effective weapons against the invaders, which may be bacteria, viruses or parasites. Other types of T-cells recognize and kill virus-infected cells directly. Some help B-cells to make antibodies, which circulate and bind to antigens.

T cells come in two different types, helper cells and killer cells. They are named T cells after the thymus, an organ situated under the breastbone. T cells are produced in the bone marrow and later move to the thymus where they mature. Helper T cells are the major driving force and the main regulators of the immune defense. Their primary task is to activate B cells and killer T cells. However, the helper T cells themselves must be activated. This happens when a macrophage or dendritic cell, which has eaten an invader, travels to the nearest lymph node to present information about the captured pathogen. The phagocyte displays an antigen fragment from the invader on its own surface, a process called antigen presentation. When the receptor of a helper T cell recognizes the antigen, the T cell is activated. Once activated, helper T cells start to divide and to produce proteins that activate B and T cells as well as other immune cells.

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Killer T cells specialized in attacking cells of the body infected by viruses and sometimes also by bacteria. It can also attack cancer cells. The killer T cell has receptors that are used to search each cell that it meets. If a cell is infected, it is swiftly killed. Infected cells are recognized because tiny traces of the intruder, antigen, can be found on their surface.

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B cell searches for antigen matching its receptors. If it finds such antigen it connects to it, and inside the B cell a triggering signal is set off. The B cell now needs proteins produced by helper T cells to become fully activated. When this happens, the B cell starts to divide to produce clones of itself. During this process, two new cell types are created, plasma cells and B memory cells.

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With the help of T-cells, B-cells make special Y-shaped proteins called antibodies. Antibodies stick to antigens on the surface of germs, stopping them in their tracks, creating clumps that alert your body to the presence of intruders. Your body then starts to make toxic substances to fight them. Patrolling defender cells called phagocytes engulf and destroy antibody-covered intruders.

The plasma cell is specialized in producing a specific protein, called an antibody, that will respond to the same antigen that matched the B cell receptor. Antibodies are released from the plasma cell so that they can seek out intruders and help destroy them. Plasma cells produce antibodies at an amazing rate and can release tens of thousands of antibodies per second.

The memory cells are the second cell type produced by the division of B cells. These cells have a prolonged life span and can thereby “remember” specific intruders. T cells can also produce memory cells with an even longer life span than B memory cells. The second time an intruder tries to invade the body, B and T memory cells help the immune system to activate much faster. The invaders are wiped out before the infected human feels any symptoms. The body has achieved immunity against the invader.

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The immune system is one of nature’s more fascinating inventions. With ease, it protects us against billions of bacteria, viruses, and other parasites. Most of us never reflect upon the fact that while we hang out with our friends, watch TV, or go to school, inside our bodies, our immune system is constantly on the alert, attacking at the first sign of an invasion by harmful organisms. The immune system is very complex. It’s made up of several types of cells and proteins that have different jobs to do in fighting foreign invaders.

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