Difference between T Cells and B Cells

The immune system fights off infection. It consists of two armies of cells; the innate and the acquired. The body’s first line of defense is the innate immune cells.

These are the cells that immediately respond to foreign organisms so as to fight infection. The next army of cell is the acquired immunity or also known as the adaptive immunity.

They invade organisms through the help of T cells and B cells. Their action takes some time but lives longer when compared to the innate cells. The T cells and B cells are the reinforcements of the body.

The body turns to T cells and B cells when it needs a more sophisticated attack.

Both T cells and B cells are lymphocytes and are manufactured in the bone marrow. B cells mature in the bone marrow while the T cells travel through the bloodstream until they reach the thymus gland where it matures. ^{(1, 2, 3)}

Image 1: T cells and B cells are both lymphocytes but have different attack/invade mechanisms.
Picture Source: askabiologist.asu.edu

Picture 2: The diagram shows how T cells and B cells functions.
Photo Source: image.slidesharecdn.com

B Cells/ B Lymphocytes

These cells fight off bacteria by creating antibodies (Y-shaped proteins). The antibody attacks a specific pathogen and has the ability to lock onto the surface of the foreign organism and mark it so that it can be identified and attacked by other immune cells. ^{(3, 4)}

T Cells/T lympocytes

These cells mature in the thymus. T cells are of two types:

• Helper T cells – These cells stimulate the B cells to produce antibodies and at the same time help in the development of killer cells.
• Killer T cells – These cells, as the name suggests directly kill the cells that are infected by foreign invaders. ^{(2, 4)}

The T lymphocytes make use of cytokines and they act as messenger molecules. They send chemical instructions to the immune system to initiate a response.

Photo 3: The image shows how T cells and B cells invade microorganisms.
Image Source: previews.123rf.com

What are the similarities between T cells and B cells?

1. They are both lymphocytes.
2. They both originate in the bone marrow.
3. They are both nucleated and motile cells.
4. They are both a part of the organism’s adaptive immune response. ^{(4, 5)}

What are the differences between the T cells and B cells?

Where they mature

B cells – In the bone marrow.
T cells – In the thymus. ⁽⁵⁾

Amount/Composition

B cells – It consists 20% of the total number of lymphocytes in the blood.
T cells – It consists 80% of the total number of lymphocytes in the blood. (3, 6)

Type of immune response

B cells – Humoral immune response
T cells – Mediated immune response ⁽⁶⁾

Ability to synthesize

B cells – They can synthesize antibodies.
T cells – They can synthesize lymphokines. ^{(6, 7)}

Cell Surface Marker

B cells – CD19
T cells – CD3 ⁽⁸⁾

Antigen binding ability

B cells – They are capable of binding to antigens.
T cells – They are not capable at binding to antigens directly. They need antigen presentation. ^{(2, 7)}

Presence of thymus-specific antigen

B cells – Absent
T cells – Present

Lifespan

B cells – Short
T cells – Long

Connections

B cells – They connect to antigens just right on the surface of the invading organisms.
T cells – They connect to virus antigens just outside of the infected cells. ^{(8, 9)}

Presence of surface antibodies

B cells – Present
T cells – Absent ⁽¹⁰⁾

Formation

B cells – They have the ability to form plasma and memory cells.
T cells – Among the cells they formed are killer, helper, and suppressor cells.

Tissue distribution

B cells – respiratory tract, germinal centers of lymph nodes, gut, spleen, subcapsular and the medullary cords of the lymph nodes.
T cells – spleen (periarteriolar) and the parafollicular area of the cortex in nodes.

Movement to the infection site

B cells – The plasma cell found in the B cells do not move to the infection site.
T cells – Lymphoblast can move to the infection site. ^{(1, 4, 7)}

Reaction to cancer cells

B cells – The plasma cells of B cells do not react against cancer cells and transplant.
T cells – Killer cells react against cancer cells and transplants.

Inhibitory effect on the immune system

B cells – They do not have an inhibitory effect on the immune system.
T cells – The suppressor cell can inhibit the immune system. ^{(3, 4)}

The table below briefly discussed the differences between T cells and B cells.

Point of Comparison	B cells	T cells
Where they mature	Bone marrow	Thymus
Composition	20% of the total number of lymphocytes in the blood	80% of the total number of lymphocytes in the blood
Immune response	Humoral	Mediated
Ability to synthesize	Synthesizes antibodies	Synthesizes lymphokines
Cell surface marker	CD19	CD3
Antigen binding ability	Can bind to antigens	Not capable at binding to antigens
Thymus specific antigen	Absent	Present
Lifespan	Short	Long
Connections	Connect to antigens on the surface of invading organisms	Connect to virus antigen outside the infected cells
Surface antibodies	Present	Absent
Formation	Can form plasma and memory cells	Can form killer, helper, and suppressor cells
Tissue distribution	Respiratory tract Germinal centers of lymph nodes Gut Spleen Subcapsular and the medullary cords of the lymph nodes	Spleen (periarteriolar) Parafollicular area of the cortex in nodes
Movement to the infection site	Plasma cell moves to the infection site	Lymphoblast moves to the infection site
Reaction to cancer cells	Do not react to cancer cells and transplant	React against cancer cells and transplant
Inhibitory effect on the immune system	Do not have an inhibitory effect on the immune system	Can inhibit the immune system

Lymphocytes are a significant part of the immune system. They are created in the bone marrow and formed into main types: T cells and B cells.

These two lymphocytes play different roles in fighting off infections. Lymphocytes leave the bone marrow.

Some of them travel to the thymus where they mature into T cells while others travel to the spleen and lymph nodes where they mature into B cells.

These two cells work differently but they have a common goal and that is to protect the body from invaders. They fight off microorganisms that can cause detrimental diseases and illnesses. ^{(4, 7, 9)}

References:

1. https://en.wikipedia.org/wiki/Lymphocyte
2. https://www.cancercenter.com/discussions/blog/whats-the-difference-b-cells-and-t-cells/
3. http://whoami.sciencemuseum.org.uk/whoami/findoutmore/yourbody/whatdoesyourimmunesystemdo/howdoesyourimmunesystemwork/whatdot-andb-cellsdo
4. http://www.biology-pages.info/B/B_and_Tcells.html
5. https://askabiologist.asu.edu/b-cell
6. https://microbiologyinfo.com/differences-between-b-cells-and-t-cells/
7. https://education.seattlepi.com/functional-difference-between-t-cells-b-cells-4573.html
8. https://www.dentalcare.com/en-us/professional-education/ce-courses/ce1/maturity-of-t-and-b-cells
9. http://www.differencebetween.net/science/difference-between-t-cells-and-b-cells/
10. https://www.verywellhealth.com/what-is-a-lymphocyte-563190

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