Unfortunately we all get ill from time to time but thankfully our bodies work very hard to ensure we don’t keep catching the same illness over and over again.

Different cells have different molecules presented on their surface to help our immune system and stop us from getting ill!

To start let’s focus on pathogens. Pathogens can come in the form of a bacterium, virus, or other microorganism that can cause disease.

Common entry points to the body for pathogens include the gas exchange surfaces and the digestive system. This is because pathogens find it easier to gain entry to organisms bodies through surfaces which exchange materials with the environment. The lungs and the small intestine are examples of these.

Examples of diseases caused by pathogens include TB and cholera. Pathogens can also cause disease by releasing toxins. For example tetanus releases a toxin to block neurones which can lead to muscle spasms.

However, to help our bodies we produce macrophages. These cells present the antigens of the pathogen on its membrane. Antigens are put on the surface of the macrophage to activate other cells in the immune system including T cells.

Antibodies are then produced which can tackle the pathogen or antigen which is making us sick!

When the body is exposed to a pathogen for the second time we do not suffer from any symptoms. This is because we are now immune thanks to the work of memory cells. They remember which antibody is needed to tackle the antigen for a second time – very useful!

Memory cells produce antibodies specific to the antigens on the pathogen very quickly and in large numbers.

Memory cells are formed after T cells have been stimulated by an antigen presenting macrophages. This in turn stimulates B cells to divide, producing plasma and memory cells.

Antibodies are made of protein. They are produced by plasma cells and bind to a specific antigen on the surface of cells.

Antibodies produced from a single group of genetically identical B plasma cells are called monoclonal antibodies.

Monoclonal antibodies can be used to target cells. This means that they can deliver certain drugs to cancer cells, to minimise the side effects on the rest of the body.