T lymphocytes and cell mediated immunity

Question 1

Define antigen

Answer 1

-Molecules which when recognised as non-self/foreign by immune system can stimulate an immune response and lead to production of antibodies
-often proteins on surface of cells

Question 2

Antigens are specific to allow immune system to identify what

Answer 2

-pathogens
-cells from other organisms of same species
-abnormal body cells
-toxins from bacteria

Question 3

Describe B lymphocytes

Answer 3

-mature in bone marrow
-associated with humoral immunity (involving antibodies that are present in body fluids or plasma)

Question 4

Describe T lymphocytes

Answer 4

-mature in thymus gland
-associated with cell-mediated immunity (involving body cells)

Question 5

Why can T lymphocytes distinguish invader cells from normal cells

Answer 5

-phagocytes that have engulfed and hydrolysed pathogen displays pathogen’s antigens on its surface membrane
-body cells invaded by virus present some viral antigens on their own cell-surface membrane
-transplanted cells from individuals of the same species have different antigens on their cell surface membrane

Question 6

What do you call cells that display foreign antigens on their surface

Answer 6

antigen-presenting cells

Question 7

What do t lymphocytes respond to

Answer 7

ONLY respond to antigens presented on a body cell (cell mediated immunity or cellular response

Question 8

Stages of response of T lymphocytes to a foreign antigen eg infected cells or cells of same species

Answer 8

-antigen from pathogen that had been engulfed by phagocytosis displays antigens of pathogen on its cell surface membrane
-specific t helper cells with receptors complementary to specific antigen thats being displayed binds to it, thus becoming activated
-binding process stimulated rapid mitosis on T cells and forms clones which:
- stimulate B cells for humoral response
- stimulate cytotoxic T cells to kill infected cells by producing perforin
- stimulate phagocytes to engulf pathogens by phagocytosis
- become memory cells

Question 9

What do cytotoxic cells kill

Answer 9

abnormal cels and body cells that are infected by pathogen

Question 10

How cytotoxic cells kill infected cells

Answer 10

-produce protein called perforin
-makes holes in cell-surface membrane
-holes mean cell membrane becomes freely permeable to all substances so cell dies as a result

Question 11

Why is the action of T cells most effective against viruses

Answer 11

viruses replicate inside cells as they use living cells
-this sacrifice of body cells prevents viruses multiplying and infecting more cells