Section 2 - Cell recognition and the immune system Flashcards
What is an infection?
An interaction between the pathogen and the body’s various defence mechanisms.
What is immunity?
When the body has already overwhelmed a pathogen and so is better prepared for a second infection from the same pathogen and can kill it before it can cause any harm.
Give examples of general and immediate defences
Skin forming a barrier Phagocytosis
What are the two types of lymphocytes?
T lymphocytes B lymphocytes
What are T Lymphocytes involved in?
Cell-mediated immune responses
What are B Lymphocytes involved in?
Humoral immune responses
How do lymphocytes recognise foreign materials?
Each cell, self or non-self, has a specific protein on their surface.
What does an antigen allow the immune system to identify?
- Pathogens - Non-self material such as skin from other organisms of the sane species. - Toxins inc bacterium causing cholera - Abnormal body cells such as cancer cells
How can you reduce the effect of tissue rejection for donors?
Donor tissues for transplants are normally matched as a closely as possible to those of the recipient. This is normally in relatives who are genetically close. Immunosuppressant drugs are often administered to reduce the level of immune response that still occurs.
What is the drug that reduces the level of immune response for transplants?
Immunosuppressant
How many different types of specific lymphocytes are there?
10 million
What is clonal selection?
When a pathogen is presented and there are already complementary lymphocytes. These lymphocytes divide and replicate.
State the reasons why lymphocytes recognise cells.
- 10 million capable of recognising different chemicals shapes - In foetus they are constantly colliding with other cells - Infection in foetus is rare as protected by mother and placenta - Therefore collide with only body’s own material (self) - Some have receptors that exactly fit those of body’s own cells - These lymphocytes either die or are suppressed - The only remaining lymphocytes are those that might fit foreign material - Any lymphocyte that shows an immune response with undergo apoptosis before they can differentiate into mature lymphocytes. - No clones of anti-self lymphocytes will appear in the blood leaving only those that might respond to non-self antigens
Why is infection in the foetus rare?
Protected from the outside by the mother and placenta.
Which lymphocytes mainly encounter self antigens?
Produced in the bone marrow.
What is apoptosis?
Programmed cell death before they can differentiate into mature lymphocytes
What is the name for programmed cell death?
apoptosis
State the two types of defence mechanisms
non specific specific
What are the characteristics of a non specific defence mechanism?
Response is immediate and the same for all pathoge ns
What are the characteristics of a specific defence mechanism?
Response is slower and specific to each pathogen
Give two examples of non specific defence mechanisms
physical barrier phagocytosis
Give two examples of specific defence mechanisms
cell-mediated response humoral response
what is a phagosome?
- In the phagocyte
- Where vesicles move the pathogen to
- Pathogen collected here to be broken down by the lysozyme
What is a lysozyme?
- Enzyme in the lysosomes that breaks down the pathogen when fused to the phagosome
Explain the stages of phagocytosis
- Pathogen produces chemicals that attract phagocyte
- Phagocyte recognises and binds to pathogen via antigen
- Phagocyte injects and engulfs pathogen vesicles move to the phagosome
- Lysosomes migrate to phagosome and combine to it
- This forms a phagolysosome containing pathogen and digestive enzyme
- Enzyme lysozyme breaks down pathogen
- Pathogen combine with glycoproteins to cell membrane and exhibits - now pathogen presenting cell which stimulates other cells in the immune response
