| Antigens | - Part of an organism that is recognised as non-self
- Triggers an immune response (usually they are proteins) |
| Types of lymphocytes | - B lymphocytes (B cells)
- T lymphocytes (T cells) |
| T lymphocytes (T cells) | - Mature in the thymus gland
- Associated with cell-mediated immunity, body cells |
| B lymphocytes (B cells) | - Mature in bone marrow
- Associated with humoral immunity, antibodies |
| Cell-mediated Immunity | - T lymphocytes recognise antigen-presenting cells that have been invaded
- Undergo mitosis to respond |
| T lymphocytes in cell-mediated immunity | - Pathogens invade body cells
- Phagocyte sticks pathogen antigens on its surface
- Receptors on helper T cell fits exactly onto antigens
- This attachment activates the T cells to divide rapidly by mitosis |
| What do the cloned T cells do | - Develop into memory cells so can rapidly respond to future infections by same pathogen
- Stimulate phagocytes to engulf pathogens
- Stimulate B cells to divide and secrete their antibody
- Activates cytotoxic T cells |
| How cytotoxic T cells kill infected cells | - Kills cells infected by pathogens
- Produces a protein, perforin
- Makes holes in the membrane
- Becomes freely permeable to all substances
- Cell dies |
