Your immune system defends the body from infection. It is made up of a complex network of cells, tissues and organs in your body. An underactive or overactive immune system can cause health issues.
The lymphatic system allows immune cells to travel between tissues and the bloodstream. The lymphatic system contains lymphocytes (white blood cells; mostly T cells and B cells), which try to recognise any bacteria, viruses or other foreign substances in your body and fight them.
Lymph nodes are found in certain areas such as the base of the neck and the armpit. They become swollen or enlarged in response to an infection.
How does the immune system work?
The skin and mucous membranes are the first line of defence against bacteria, viruses and other foreign substances. They act as a physical barrier, and they also contain immune cells.
When your skin has a cut, harmful microbes (tiny particles) can enter and invade your body. The cut triggers certain immune cells in the bloodstream that try to destroy the invaders.
In an infection, white blood cells identify the microbe, produce antibodies to fight the infection, and help other immune responses to occur. They also ‘remember’ the attack.