T lymphocytes and cell-mediated immunity

Antigens:

• Any part of an organism or subtance that is recognised as foreign by the immune system and stimulates an immune respone
• Usually proteins that are part of the cell-surafce membrans or cell walls of invading cells such as micro organisms or abnormal body cells
• The presence of an antigen triggers the production of an antibody as part of the body's defence systems

Lymphocytes:

• Produced by stem cells in the bone marrow

T lymphocytes -

• Mature in the thymus gland
• Associated with cell-mediated immunity that is immunity involving body cells

Cell-mediated immunity: (cellular response)

• T lymphocytes will only respond to antigens that are presented on body cells
• The receptors on each T cell respond to a single antigen

Stages in the response of T lymphocytes to infection by a pathogen -

• Pathogens invade body cells or are taken in by phagocytes
• The phagocyte places antigens from the pathogen on its cell-surface membrane
• Receptors on a specific T cell (Th cell) fit exactly onto these antigens
• This attachment activates the T cell to divide rapidly by mitosis and form a clone…