T-LYMPHOCYTES AND CELL MEDIATED IMMUNITY Flashcards
What is an antigen
any part of an organism or substance that is recognised as non-self by the immune system
What are lymphocytes produced by
stem cells in the bone marrow
What are the 2 types of lymphocytes
1) B lymphocytes
2) T lymphocytes
Where do B lymphocytes mature
bone marrow
Where do T lymphocytes mature
thymus gland
What type of immunity are B lymphocytes associated with
humoral immunity
What type of immunity are T lymphocytes associated with
cell-mediated immunity
How do T lymphocytes distinguish foreign cells from normal cells (4 points)
1) phagocytes that have engulfed and hydrolysed pathogens present their antigens on their own cell-surface membrane
2) body cells invaded by a virus present antigen on cell-surface membrane
3) transplanted cells have different antigens on surface
4) cancer cells present antigens on surface
What are antigen-presenting cells
cells that display foreign antigens on their surface
What do the receptors on the T cells do
respond to a single antigen
What is the response of T-lymphocytes to infection by a pathogen (5 points)
1) pathogens invade body cells or are taken in by phagocytes
2) phagocyte places antigens from pathogen on its cell-surface membrane
3) receptors on helper T-cells fit onto antigens
4) attachment activates the T cell to divide rapidly by mitosis to form a clone of genetically identical cells
5) the cloned T cells either:
a) develop into memory cells that enable a rapid response to future infections
b) stimulate phagocytes to engulf pathogens
c) stimulate B cells to divide and secrete their antibody
d) activate cytotoxic T cells
How do cytotoxic T cells kill infected cells
by producing a protein called perforin that makes holes in the cell-surface membrane that mean it becomes freely permeable to all substances so it dies
What is bird flu caused by
strain of the influenza virus
