The immune system in defence against diseases

• Pathogens are disease-causing viruses, bacteria, fungi or protists, which can infect animals and plants.
• Humans have an immune system, which can defend them from pathogens.
• The immune system of the human body in defence against disease includes two types of white blood cell: phagocytes and lymphocytes.
• Phagocytes are cells, such as white blood cells, that engulf and absorb waste material, harmful microorganisms, or other foreign bodies in the bloodstream and tissues.
• Lymphocytes are white blood cells which attack pathogens by producing antibodies.
• Phagocytes surround any pathogens in the blood and engulf them, they are attracted to pathogens and bind to them.
• The phagocytes membrane surrounds the pathogen and enzymes found inside the cell break down the pathogen in order to destroy it.
• Phagocytes are called 'non-specific' as they do this to all pathogens that they encounter.
• Lymphocytes recognise proteins on the surface of pathogens called antigens, these are foreign not naturally occurring within your body and produce antibodies.
• The antibodies cause pathogens to stick together and make it easier for phagocytes to engulf them.
• Some pathogens produce toxins, which make you feel ill, lymphocytes can also produce antitoxins to neutralise these toxins.
• Both the antibodies and antitoxins are highly specific to the antigen on the pathogen, thus the lymphocytes that produce them are called 'specific'.