5. Cell Recognition And The Immune System Flashcards
What must a pathogen do if it is to infect the body?
Gain entry to the body
What is the body’s first line of defence?
To form a physical or chemical barrier to entry
What is the body’s second line of defence?
The white blood cells
What are the body’s two types of white blood cells used in defence?
Phagocytes and Lymphocytes
What are phagocytes?
Ingest and destroy the pathogen in a process called phagocytosis before it can cause harm
What are lymphocytes?
Involved in immune responses
What is phagocytosis?
Where large particles can be engulfed in the vesicles formed from the cell surface membrane
What is the first process of phagocytosis?
- chemical products of pathogens or dead damaged and abnormal cell act as attractant causing phagocytes to move toward the pathogen
What is the second stage of phagocytosis?
Several receptors on their cell surface membrane that recognise and attach to chemicals on the surface of the pathogen
What is the third stage of phagocytosis?
They engulf the pathogen to form a vesicle called a phagosome
What is the fourth stage of phagocytosis?
Lysosomes move towards the vesicle and fuse with it
What is the fifth stage of phagocytosis?
The lysozymes destroy ingested bacteria by hydrolysis of their cell walls
What is the sixth stage of phagocytosis?
The soluble products from the breakdown of the pathogen are absorbed into the cytoplasm of the phagocytes
What is an infection?
An interaction between the pathogen and the body’s various defence mechanisms
What two things can happen when the body gets infected?
- the pathogen can overwhelm the defences and the individual dies
- the body’s defence mechanisms overwhelm the pathogen and the individual recovers from the disease`
What is immunity?
When the body’s defences are better prepared for a second infection from the same pathogen and can kill it before it can cause any harm
What are two ways the body protects itself from pathogens?
- General and immediate
- More specific less rapid but long lasting
What is the general and immediate way of protecting the body from pathogens?
The skin - forms a barrier to the entry of pathogens and phagocytosis
What is the more specific, less rapid but long lasting way of protecting the body from pathogens?
Types of white blood cell called lymphocyte that takes place in two forms :
- Cell-mediated responses involving T lymphocytes
- Humoral responses involving B lymphocytes
What must the lymphocytes be able to do to defend the body from invasion by foreign material?
They must be able to distinguish the body’s own cells and molecules from those that are foreign else they would destroy the organisms own tissues
How are cells recognised as self or non self by the lysosomes?
Each cell have specific molecules on its surface that identify it, the molecules can be a variety of types but its the proteins are the most important
What structure do the proteins on the cell surface have?
They have enormous variety and a highly specific tertiary structure, this allows them to be distinguished against other cells
What do the proteins allow the immune system to identify?
- Pathogens - HIV
- Non self material - cells from other organisms of the same species
- Toxins - those produced by certain pathogens like the bacterium that cause cholera
- Abnormal body cells such as cancer cels
What does the immune system do when it recognises organ transplants from a non self organism?
It attempts to destroy the transplant
