To work properly, your immune system needs to be able to tell the difference between ‘good’ cells (your own healthy cells) and ‘bad’ cells (bugs, human cells infected with viruses or cancer cells). If you have a weakened immune system, it will not recognise or fight the ‘bad’ cells as well as it should. This means that you are more likely to get infections or to develop cancer. Examples of situations where your immune system is underactive include people suffering HIV/AIDS, people taking immune suppressing drugs to allow an organ transplant (e.g. a kidney transplant) or people taking long-term steroids to treat diseases e.g. chronic bronchitis.
When we talk about our immune system we are describing a wonderfully complex network of organs, cells and molecules that protect us from infection and disease. When your immune system is working as it should, it recognises abnormal cells, harmful “bugs” (infectious organisms that can cause disease) and destroys