5.3 T Lymphocytes And Cell Mediated Immunity Flashcards
What is an antigen?
The proteins found on the cell-surface membrane or cell wall of an invading cell that is recognised as non-self that stimulate an immune response
T lymphocytes
- mature in the thymus gland
- associated with cell-mediated immunity
How do T cells distinguish whether a cell is foreign or not?
- Phagocytes present some of the pathogens antigens on their cell-surface membrane
- body cells invaded by viral cells present some of the viral antigens
- transplanted cells have different antigens
- cancer cells are different from normal body cells and present antigens
What are cells that display foreign antigens on their surface called?
Antigen-presenting cells
What do T lymphocytes respond to? What is this usually called?
- only respond to antigens presented on a body cell
- usually called cell-mediated immunity or the cellular response
What are the 5 main stages in the response of T lymphocytes to infection by a pathogen?
1) Pathogens invade body cells or are taken in by phagocytes
2) Phagocyte presents antigen on cell-surface membrane
3) Receptors on specific helper T cell fit exactly onto antigens
4) Activates the T cell to divide rapidly by mitosis
5) The cloned T cells:
- develop into memory cells
- stimulate phagocytes to engulf pathogens
- stimulate B cells to divide and secrete their antibody
- activate cytotoxic T cells
What do the cloned T cells do?
The cloned T cells:
- develop into memory cells
- stimulate phagocytes to engulf pathogens
- stimulate B cells to divide and secrete their antibody
- activate cytotoxic T cells
How do Cytotoxic T cells kill pathogens?
They produce a protein called PERFORIN that makes holes in the cell-surface membrane of the pathogens, resulting in the cell dying because the cell membrane becomes freely permeable.
What does perforin do?
It creates holes in the cell-surface membrane of a pathogen, resulting in the cell dying.
