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Difference Between T Cells And B Cells

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The human body has got a strong immune system that protects us from all deadly infections and diseases. They do so with the help of immune cells that fight together to protect us. B cells and T cells are two crucial immune cells or lymphocytes that defend us against numerous diseases or pathogens. Both cells are produced by the bone marrow, but they do not mature there. The main lymphoid organs are the thymus and bone marrow. The lymphocytes that continue to remain in the bone marrow for differentiation are known as “B-cells,” whereas the lymphocytes that migrate to the thymus are referred to as “T-cells.”  Their mode of action against fighting pathogens is different.  For example- when any pathogen enters the body, T cells recognize them and stimulate different T cells (Helper T-cells, Suppressor T-cells, Memory T-cells, Killer T-cells) and start making clones.  This is how they increase their number and fight against pathogens.  However, the B cells, are first activated by T cells, and they also start multiplying and creating copies of memory B cells and plasma cells that migrate to the infection site (lymph).  If the same virus or bacterium re-infects a person, memory B cells can promptly eliminate the antigens. 

What are T Cells?

These lymphocytes control the immunological response mediated by cells, making up around 75% of the circulating lymphocytes. They originate from bone marrow hemocytoblasts, and when they move to the thymus, they are referred to as T-cells. These immature cells, known as thymocytes in the thymus, develop into T lymphocytes. Thymosin, a local polypeptide hormone, encourages this maturation process. 

Mode of Action of T Cell

When T cells recognize a specific antigen, it stimulates different T cells. After being stimulated, the T cell divides rapidly and forms a clone of cells known as lymphoblasts. These clones are morphologically similar and can react specifically with the same antigen but perform different functions.  Four different T-lymphocyte subtypes are present in the clone:

  1. Helper T-cells: Sensitized helper T-cells create lymphokines to carry out a variety of tasks, such as promoting the growth of other T cells and activating macrophages and B lymphocytes.
  2. Suppressor T-cells: These cells prevent the immune system from an attack on the body’s own cells.
  3. Memory T-cells: These are previously sensitized cells with long-term memory of the sensitization.
  4. Killer T-cells, also known as cytotoxic T-cells: Are immune system cells that obliterate cancer cells, infected bodily cells, and other foreign invaders. Perforins are secreted after killer T cells attach to infected cells. The infected cell then develops a hole thanks to perforins. The label “cytotoxic T-cell” comes from the fact that it also releases chemicals that kill the cell.

What are B Cells?

One of the immune cells that are in charge of producing antibodies and providing humoral immunity is the B cell or lymphocyte. They make up 25% of all lymphocytes. They release cytokines that draw in additional immune cells. In reaction to the antigens, these cells develop in the bone marrow and create antibodies. The humoral reaction involves B lymphocytes. B cells create memory B cells and plasma cells as soon as they come into contact with antigens. Therefore, B cells create antibodies or immunoglobulins (Ig) that are targeted at the pathogens that have infiltrated the body. The bone marrow produces new B-lymphocytes every few days since they have a short lifespan.

Mode of Action of B Cells

Both helper T-cells and antigens immediately sensitize B-lymphocytes. B lymphocyte that has been activated quickly divides to create copies of memory B cells and plasma cells. Antibody production occurs in plasma B cells, sometimes referred to as effector cells. Specialized cells called plasma cells make protective proteins and release them into the blood. The plasma cells act through a fluid rather than migrating to the infection site (lymph). They are referred to as the humoral immune system since humor in Latin means liquid. If the same virus or bacterium re-infects a person, memory B cells can promptly eliminate the antigens since they have a lengthy lifespan. The antibody molecules might stay free or bind to a cell membrane.

Differences Between B-Cells and T-Cells

S.No

Characteristics

B cells

T cells

1 Another name B lymphocytes T lymphocytes
2 Maturation Bone marrow Thymus
3 Percentage in the Blood 25% of the blood lymphocytes 75% of the blood lymphocytes
4 Lifespan short long
5 Type of Immunity Humoral or antibody-mediated immunity (AMI) cell-mediated immunity (CMI)
6 Types Two types (plasma cells and memory cells) Three types (helper T cells, cytotoxic T cells, and suppressor T cells)
7 Recognition of pathogen It can recognize both bacterial and viral antigens It can only recognize viral antigens
8 Secretion Antibodies Lymphokines
9 The movement to the Infected Site Show movement to the site of infection. Do not show movement to the site of infection.
10 Presence or absence of surface antigens Absent Present
11 Defend against The B cells defend against bacteria and viruses in the bloodstream or lymph. The T cells defend against pathogens including viruses, protists, and fungi that enter the cells in the body.
12 Location in lymph nodes Outside Inside
13 Membrane Receptor B cell receptor (BCR) T cell receptor (TCR)
14 Inhibitory effect on the immune system The suppressor cells inhibit the immune system. They have no inhibitory effect on the immune system

Similarities Between B cells and T cells

  1. Both are lymphocytes, therefore known as B and T lymphocytes.
  2. Both are produced in the bone marrow.
  3. Both fight against pathogens through different immunity mechanisms.
  4. Both have antigen receptor sites on them. For example-BCR in B cells and TCR in T cells.
  5. Both are motile and consist of a large nucleus.
  6. Both are found in lymphoid organs.
  7. Both multiply in bulk so that they can give a tough fight to pathogens.

Conclusion

B and T cells are of immune cells that protect us from invading pathogens by adopting different mechanisms. B cells adopt Humoral or antibody-mediated immunity (AMI) whereas T cells adopt cell-mediated immunity (CMI) to kill the pathogens. However, the basic principle remains the same both multiply themselves to kill pathogens. Nevertheless, B cells depend upon T cells for stimulation. Both B cells and T cells vary in terms of abundance in blood, types of receptors, their maturation site, lifespan, etc. Despite so many differences, they have similarities also, like- both are types of lymphocytes, found in lymphoid organs, motile and nucleated, etc.

FAQs

Q1. What is the origin of B and T cells?

Ans. Bone marrow

Q2.  What are lymphoid organs?

Ans. The organs responsible for the production of immune cells are called lymphoid organs.

Q3. What is the bursa of Fabricius?

Ans. The Bursa of Fabricius is gut-associated bursal lymphoid tissue where B cells mature. It is found in vertebrates.

Q4. What is the role of suppressor T cells? 

Ans: The suppressor T cells terminate the whole immune response due to which the body’s own cells are prevented from the attack by the immune system. This mechanism is also known as immune tolerance.

Q5. What do B in B cells and T in T cells indicate?

Ans. B in B cells indicate bone marrow whereas T in T cells indicates Thymus. Both bone marrow and thymus are the locations where they get mature.



Last Updated : 02 Mar, 2023
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