5: Cell recognition and the immune system Flashcards
A lymphocyte is a type of white blood cell, what are the two forms?
- cell mediated responses involving T lymphocytes
- humoral responses involving B lymphocytes
the specific tertiary structured proteins on cells allow the immune system to identify?
- pathogens
- non-self material
- toxins
- abnormal body cells
are lymphocytes produced in responses to an infection, or already exists
already exist. there are millions so there will be one lymphocyte with a complementary protein to a complementary protein on a pathogen
how lymphocytes recognise cells from your own body
- in fetus, lymphocytes constantly colliding with cells
- infection is rare in fetus as protected by placenta in mother
- some lymphocytes will have receptors that fit those of own body cells - this are killed
- the remaining owning respond to foreign material
- any that show immune response undergo programmed cell death before they can differentiate into mature lymphocytes
two types of white blood cells:
- lymphoctyes (immune response)
- phagocytes (phagocytosis)
Process of phagocytosis (non specific defence mechanism like physical barriers)
- chemical products of pathogen act as an attractent to the phagocyte
- so move towards
- phagocytes have receptors that recognise and attach to these chemicals
- engulfs pathogen to form a vesicle called a phagosome
- lysosomes move towards vesicle and fuse with it
- enzymes lysozymes destroy ingested bacteria by breakdown of cell walls by hydrolysis
- the soluble products from breakdown are absorbed into phagocyte cytoplasm
Antigen
part of an organism that is recognised as non self by the immune system and so stimulates an immune response
Specific defence mechanism
- lymphocytes
slower but provide long term immunity, they are produced by stem cells in bone marrow
B lymphocytes
- mature in bone marrow
- humoral immunity, which involves antibodies present in body fluids
T lymphocytes
- mature in thymus gland
- associated with cell mediated immunity (involving body cells)
Cell mediated immunity
- respond to own cells affected by non-self material (virus)
- respond to non-self cells, which have different antigens than own.
T lymphocytes can distinguish these invade cells by - phagocytes present the pathogens antigens
- body cells invaded by virus present virus antigens
- transplanted cells have diff antigens presented than our own
- cancer cells are different than normal cells and present antigens
(cells displaying foreign antigens = antigen-presenting cells)
stages in response of T lymphocytes to infection from pathogen
1 - pathogens invades body cells or taken in by phagocyte
2 - phagocytes presents pathogens antigens on cell membrane
3 - receptors on specific t cell fit exactly to these antigens
4 - t cell divides rapidly by mitosis
5 - clone t cells turn into memory cells for rapid response, stimulates phagocytosis, stimulates b cells to divide and secrete antibody, activate cytotoxic t cells
how do cytotoxic t cells kill infected cells
produces protein that makes holes in cell membrane of infected cells
T cells =
cell mediated response
B cells =
humoral immunity