Defence mechanisms Flashcards
Define pathogen and give examples
A pathogen is a microorganism that causes disease. Examples include bacteria, viruses, fungi and protists.
Define antigen
Any part of cell surface membrane (usually a protein) that can be recognised by the immune system and can stimulate an immune response.
Describe the first line of defence
Physical and chemical barriers
Describe the second line of defence
Phagocytosis
Describe what is meant by immunity
Immunity is where an organism is no longer susceptible to a
particular disease
What are the 2 types of immunity called
- Active immunity
- Passive immunity
Describe what is meant by active immunity
Active immunity is where the resistance to disease is caused by the activities of a person’s own immune system.
Pros and cons of active immunity
Pros - Long lasting protection, the body has produced memory cells
Cons - Takes longer as the body has to produce memory cells and antibodies in response to a foreign antigen
Describe how active immunity can be naturally acquired
An encounter with the pathogen
Describe how active immunity can be artificially acquired
Through the use of a vaccination
Describe what is meant by passive immunity
Passive immunity is when resistance to the disease is acquired from the introduction of antibodies from another individual, rather than an individual’s own immune system
Pros and cons of passive immunity
Pros - Immediate protection
Cons - Short-lived, the body is unable to produce its own antibodies
Describe how passive immunity can be naturally acquired
Through the mother’s milk/across the placenta,
Describe how passive immunity can be artificially acquired
Through injections with the necessary antibodies and is usually used to treat diseases that are difficult to build an immune response to.
What cells are used by the specific part of the immune system
Lymphocytes
State the 2 types of lymphocytes and their function
- T lymphocytes are involved in the ‘cell mediated response’
- B lymphocytes are involved in the ‘humoral reponses’
Describe what lymphocytes are and explain their uses
- lymphocytes use a structure called
‘antigens’ to identify between their own cells and molecules (referred to as ‘self) versus those that are foreign (or, ‘non-self’). If it wasn’t for these antigens, the body would destroy its own tissues. - Each type of cell has specific molecules on its surface that identify it, but it is the proteins that are most important. This is due to its highly specific 3D tertiary structure
They help us to identify: pathogens, non-self material from other organisms of the same species, toxins and abnormal cells e.g. cancer cells.
Why do people who need organ transplants have to take immunosuppressant drugs?
- When somebody has an organ transplant, they are accepting foreign material from another organism. This means that they antigens present will be different to their own, even if this organism is of the same species, and their body will recognise this as ‘non-self’. Their immune system will begin to attack and causes tissue rejection.
In order to minimise this, donors are usually relatives who have closely matched DNA. However, this still isn’t enough, so immunosuppressant drugs are given (Immuno
immune system, suppressant - stop/prevent/weaken)
This reduces the level of immune response that occurs.
