Unit 2 - Cell Recognition and the Immune System Flashcards
Immunity
The body’s ability to identify and protect itself against disease
Immune System
- The system in the body responsible for maintaining homeostasis
- Does this by recognising organisms from non-harmful organisms and produces a response
Pathogens
Any organism that causes disease/an immune response to its host
2 Main types of Defence Mechanisms
- Specific Defence Mechanisms
- Non-Specific Defence Mechanisms
Non-Specific Defence Mechanisms
- Doesn’t distinguish between one pathogen and another
- Responds to all pathogens in the same way
2 Types of Non-Specific Defence Mechanisms
- Barriers to entry
- Phagocytosis
Barriers to entry
- Skin
- Saliva and Tears
- HCL Stomach Acid
- Mucus and Cilia Cells
How does the Skin act as a Barrier to Entry?
- It covers the entire body and acts as a physical barrier
- It secretes antimicrobial substances
- When the skin is cut, platelets clot and dry out to form a scab at the site of the wound
How do Saliva and Tears act as a Barrier to Entry?
- Saliva and Tears contain lysozymes
- These lysozymes are able to destroy bacteria cells by hydrolysing their cell walls
How do Mucus and Cilia Cells act as a Barrier to Entry?
- Goblet cells (found in the trachea) produce mucus, which is able to trap pathogens
- The mucus is wafted up the trachea by cilia cells in the trachea towards the throat
How does the Nose act as a Barrier to Entry?
- Nose hairs act as a physical barrier to pathogens
- Cells in the nose produce mucus which traps pathogens
- When you blow your nose, the pathogens are removed with the mucus
How does HCL Acid in the Stomach act as a Barrier to Entry?
HCL Acid lows the pH of the stomach which kills microbes
Phagocytosis
- Chemotaxis (phagocytes (neutrophils) detect chemokines released by the pathogen and move towards it)
- Phagocyte attaches to to the surface of the pathogen
- Phagocytes engulfs the pathogen to form a phagosome (phagocytic vesicle)
- Lysosomes move to the pathogen, fuse with it and release lysozymes into it
- Lysozymes hydrolyse the pathogen
- The breakdown products are absorbed by the phagocyte or leave it
- The neutrophils die (accumulation of pus signals dead neutrophils
Antigen
Foreign protein on the surface of an organism that stimulates an immune response
Specific Defence Mechanisms
- Does distinguish between different pathogens
- Creates long lasting immunity
2 Types of Specific Defence Mechanisms
- Cell-Mediated Responses (involve T-lymphocytes)
- Humoral Responses (involve B-lymphocytes)
Cell Mediated Response
- Macrophage engulfs pathogen and presents itself on it’s surface (macrophage is an antigen presenting cell now)
- T-cell receptors on the T-helper cell attach to the pathogen and activate the T-helper so it undergoes mitosis
- Interleukins are produced (they trigger more phagocytes to increase phagocytosis rate and stimulate B-cells to divide by mitosis)
- Interleukins trigger division of T-killer cells (release perforin which destroys pathogen cell membrane making it free-permeable and unable to survive)
Humoral Immunity
- B-cell engulfs pathogen and presents it on its cell surface
- T-helper attaches to the B-cell to activate it
- Stimulates plasma cells to divide (produce and secrete antibodies that attach to the antigen of the pathogen and destroy it)
- Stimulates memory cells to divide (respond to future infection by the same pathogen
Antibodies
- Proteins made by B-lymphocytes in response to the presence of a specific antigen
- Complementary to a specific antigen
Structure of Antibodies
- 4 polypeptide chains (2 heavy chains (long) and 2 light chains (short) )
- ## Specific antigen binding site that antigens bind to and form antigen-antibody complex
