Fighting back
Human immunity
The immune system defends the body against disease.
If Microorganism that causes disease. pass the non-specific first line of defence they will cause an infection. However, the body has a second line of defence to stop or minimise this infection. This is called the The body's defence system against entry of any foreign body, including pathogens and agents such as pollen grains. The role of the immune system is to prevent disease..
All cells have proteins called antigens on their surfaces. All cells have molecules that can trigger an immune response, called A protein on the surface of a substance (often a pathogen) that triggers an immune response.. Antigens can be used for recognition. White blood cells are able to attack pathogens because they have antigens that are recognised as 'non-self'. Antigens on body cells are recognised as 'self'.
White blood cells
One type of white blood cell is attracted to pathogens and bind to them. Then they ingest and digest the pathogen.
As they do this to all pathogens that they encounter, we call them 'non-specific'.
Antibodies
Another type of white blood cell makes antibodies. These white blood cells can distinguish between 'self' and 'non-self (foreign) antigens. This means that they can detect if proteins on the surface of pathogens are foreign or do not naturally occur within the body and they then produce A protein produced by the immune system in humans (and other animals) that attacks foreign organisms (antigens) that get into the body..
Each white blood cell makes only one type of antibody. Each type of antibody attaches to only one specific antigen. The organism must make different antibodies for each type of pathogen. The antibodies cause pathogens to stick together and make it easier for white blood cells to engulf them.
The immune response
There are some diseases you can only catch once. This is because your body has developed immunity to them. The reason this happens is that memory cells stay in your blood. These are white blood cells from your first immune response. They can remain for many years, and mean that you have a faster immune response if you are exposed to the pathogen again because antibodies can be made as soon as the pathogen appears.
Plant defence responses
Just like animals, plants are constantly defending themselves from attack from Microorganism that causes disease.. Again like us, plants have physical and chemical defences which stop pathogens from infecting them and causing disease.
Physical defences
Many plants are covered with a thick bark. This is an external layer of dead cells which forms a physical barrier against infection. In this way it is very much like our skin. Beyond bark, each plant cell has a A carbohydrate. It forms the cell wall in plant cells. cell wall which acts as another barrier against infection. Leaves are covered with a waxy The outer layer of a leaf which protects it. which also stops their cells from becoming infected.
Chemical defences
Some plants, such as mint and witch hazel, produce A substance that kills or inhibits the growth of microorganisms. chemicals. These limit the spread of Single-celled microorganisms, some of which are pathogenic in humans, animals and plants. Singular is bacterium. and other pathogens that were not stopped by physical defences. We now use these chemical defences in antiseptics for humans.
Other defences
Farmers can now Process which involves the artificial transfer of genetic information from one donor cell or organism to another. crop plants to be resistant to infections.