Section 2 - Chapter 5: Cell recognition and the immune system Flashcards
1
Q
What are Antigens
A
- Are molecules (usually proteins) on the surface of cells that can generate an immune response when detected by the body
- Antigens not found on the body are known as foreign antigens and allow the immune system to identify
- Pathogens
- Abnormal body cells
- Toxins
- Cells from other individuals of the same species
2
Q
What are Pathogens
A
- Are organisms that cause disease
- All pathogens have antigens on their surface and are foreign by the immune system which respond
3
Q
What are Abnormal body cells
A
- Cancerous or pathogen-infected cells that have abnormal antigens on its surface which trigger an immune response
4
Q
What are Toxins
A
- These are poisons
- Some toxins are produced by bacteria. The immone system can respond to toxins and their releasers.
5
Q
What are cells from other individuals of the same species
A
- Organ transplant/ blood transfusion
- Those cells will have some antigens different from your own
- The foreign anigens will trigger an immune response - leads to rejection of transplanted organ if drugs aren’t taken to suppress the system
6
Q
What is Antigenic Variation
A
- Antigens activate primary response so when infected again with same pathogen (same antigens on surface) they activate secondary response
- However antigens may change their surface antigens - Antigenic Variation (Formed due to changes in the genes of a pathogen)
7
Q
What is the effect of Antigenic Variation
A
- This means that when you are infected for a second time, the memory cells produced from the first infection will not recognise the different antigen
- So immune system has to start again mounting primary response
- Also makes it harder to develop vaccines against some pathogens
- Examples: HIV, Influenza virus
8
Q
What is the main stages of the immune response
A
- Phagocytosis
- T-Cells - Phagocytes activate T-cells
- B-Cells - T-cells activate B-cells which divide into plasma cells
- Antibody production - plasma cells make antibodies for a specific antigen
9
Q
What happens in Phagocytosis
A
- A phagocyte is a type of WBC that carries out phagocytosis
- A phagocyte recognises foreign antigens
- These acts as attractants causing phagocyte to move towards pathogen
- Phagocytes have receptors on their cell-surface membrane that attach to chemicals on pathogen
- They engulf pathogen to form a vesicle - phagosome/phagocytic vacuole
- Lysosomes move towards the vesicle and fuse with it
- Enzymes called lysozymes destroy ingested bacteria by hydrolysis of cell walls
- The soluble products of the breakdown are absorbed by cytoplasm of phagocyte
- The phagocyte presents pathogen’s antigens on its cell surface membrane to activate other immune system cells (antigen-presenting cell)
10
Q
What are Lymphocytes and what are the 2 types
A
- Phagocytosis is non-specific and a lymphocyte is a type of White blood cell that has specific responses and provide longer term immunity
- Are produced by Stem cells in the bone marrow
- B-Lymphocytes
- T-Lymphocytes
11
Q
What are T-Cells and what do they do
A
- Mature in the Thymus Gland
- It has receptor proteins on its surface that bind to complementary antigens presented to it by phagocytes that activate the helper T-Cell and causes it to divide by mitosis to produce clones.
- It can stimulate and activate other cells
- Known as cell-mediated immunity
12
Q
What are the types of cells that a T-Helper cell can activate and stimulate
A
- Activate Cytotoxic cells - which kills abnormal and foreign cells
- Stimulate B-Cells - to divide and secrete antibody
- Stimulate phagocytes - engulf pathogens in phasgocytosis
- Develop into memory cells to enable rapid response to future infection
13
Q
What is a B-cell and what does it do
A
- Type of WBC that has antibodies that bind with antigen to form antigen-antibody complex
- When the antibody on the surface of a B-cell meets a complementary shaped antigen it binds to it. and the antigens are presented on the surface.
- T helper cell binds to the antigen and stimulate it to divide by mitosis
- This process is called clonal selection and the activated B-cell divides into plasma cells
14
Q
What are plasma cells and what are memory cells
A
- Are identical to B-cells and secrete lots of antibodies specific to the antigen - monoclonal antibodies and form lots of antigen-antibody complexes - primary immune response
- Are responsible for secondary immune response - when the encounter antigen they rapidly divide into plasma and more memory cells. Longer tem immunity
15
Q
What does Agglutination mean
A
- An antibody has 2 binding sites so can bind to 2 pathogens at the same time
- This means pathogens become clumped together this is called agglutination
- Phagocytes can phagocytose many pathogens at once