B-Lymphocytes and T-Lymphocytes (Leaving Cert Biology): Revision Notes

B-Lymphocytes and T-Lymphocytes

• Lymphocytes are a type of white blood cell. They play an important role in the immune response.
• All lymphocytes are made in the bone marrow.
• Depending on where they mature, lymphocytes are divided into 2 main groups;
  • B-cells.
  • T-cells.

B Cells

• B-cells are the lymphocytes responsible for producing antibodies.
• Humans are born with millions of different B-cells.
• B-cells mature in the bone marrow.
• Once mature, they move to the lymph nodes**.**
• Each B-cell produces a specific antibody with a unique shape, which is displayed on its surface.
• When a B-cell's antibody matches an antigen, the B-cell multiplies (clones) and produces large quantities of the specific antibody.
• After the infection is overcome, most B-cells die, but a small number remain as memory B-cells.
• These provide long-term immunity by responding quickly to future infections by the same pathogen.

T Cells

• T-cells mature and are activated in the thymus gland (T for thymus).
• T-cells do not produce antibodies.
• There are four types of T-cells:

1. Helper T-cells
2. Killer T-cells
3. Suppressor T-cells
4. Memory T-cells

1. Helper T-Cells

• Helper T-cells multiply and release chemicals to stimulate (help) B-cells to multiply.
• These B-cells then produce the correct antibodies.
• Helper T-cells also stimulate the production of killer T-cells.

2. Killer T-Cells

• Killer T-cells attack and destroy abnormal body cells, including infected and cancerous cells.
• Also known as natural killer (NK) cells because they are cytotoxic (cell-killing).

3. Suppressor T-Cells

• Suppressor T-cells inhibit the activity of B-cells and other T-cells.
• Suppressor T-cells become active after the pathogens are destroyed.
• In this way, they turn off the immune response once the infection is under control, preventing damage to healthy tissue.

4. Memory T-Cells

• Memory T-cells stimulate B-cells and killer T-cells to multiply if the same antigen enters the body again.
• After an infection, memory T-cells can live for years or even a lifetime, providing immunity to future infections by the same pathogen.