Chapter 5 Cell recognition and immune system Flashcards
What are the two types of defence mechanisms.
Cell mediated response involving T lymphocytes
Humoral respoense involving B lymphocytes
What are self cells
The body’s own cells and molecules
What are non-self cells
Cells or molecules that are foreign
Why is it important that the immune system can tell the difference between self cells and non-self cells
to defend from foreign materials
not destroy the organism’s own tissues when defending itself
What is the problem with organ/tissue transplants in humans, how can we solve this?
The immune system recognises the transplant as non-self and begins to attack the transplanted tissue
SOLUTIONS:
tissue matching (e.g. from relatives)
immunosuppressant drugs
Describe how lymphocytes are able to identify cells as ‘self’ or ‘non-self’
lymphocytes have receptors that exactly fit those of the body’s own self cells
these lymphocytes are destroyed/suppressed
only ones that stay are the ones that fit foreign material (non-self)
What are the 4 things that the immune system can identify
pathogens
non-self material
toxins
Tumors
Describe the process of phagocytosis
- the phagocyte is attracted to the pathogen and it moves towards the pathogen along a conc. gradient
- the phagocyte has several receptors on its CSM that attach to chemicals on the surface of the pathogen
- phagocyte then engulfs the pathogen forming a phagosome
- lysosomes within the phagocyte migrate towards the phagosome
- the lysosome release their lysozymes into the phagosome, where they hydrolyse the pathogen’s cell walls, destroying it
- the soluble products from the breakdown of the pathogen are absorbed into the cytoplasm of the phagosome
- other cell debris is moved out of the cell by exocytosis
Where can phagocytes be found
In the blood
Which cells do phagocytes activate
T-cells (they bind their own receptors to the complimentary antigens on the surface of phagocytes (antigen presentation))
What are antigens
Proteins that are located on the surface of cells which can trigger an immune response when detected by lymphocytes
What does the presence of antigens trigger
Presence of antigens triggers a production of antibodies or other specific immune response
What are the 2 types of lymphocytes and where do they develop
T cells: produced in bone marrow, mature in thymus gland
B cells: produced and matured in bone marrow
How can T lymphocytes distinguish invader cells from normal cells
phagocytes that have engulfed and hydrolysed a pathogen present some of a pathogen’s antigens on their own CSM
body cells invaded by a virus present some of the viral antigens on their own CSM
transplanted cells from individuals of the same species have different antigens on their CSM
Caner cells are different from normal body cells and present antigens on their CSM
What is cell-mediated immunity
When the T helper lymphocytes only respond to antigens that are presented on a body cell
What are the steps in a lymphocyte responding to an antigen
- 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 helper T cell (T cell) fit exactly onto these antigens.
- This attachment activates the T cell to divide rapidly by mitosis and form a clone of genetically identical cells.
5 The cloned T cells:
- develop into memory cells that enable a rapid response to future infections by the same pathogen
- stimulate phagocytes to engulf pathogens by phagocytosis
- stimulate B cells to divide and secrete their antibody
- activate cytotoxic T cells (Tc cells).
What do cytotoxic cells do
kill abnormal cells and any infected body cells
they produce a protein called perforin
it makes holes in CSM, compromising
the holes means = cell membrane becomes freely permeable to all substances and the cell dies as a result