human defence systems 3.1.6

• there are various ways in which the body prevents pathogens from entering the body such as mucus in nose, skin and scabs, the immune system, stomach acid to kill bacteria, expulsive reflexes and earwax in ears
• there are two types of white blood cells called lymphocytes -B and T cells- and phagocytes
• the immune system is the body system which recognises and destroys foreign cells of proteins, such as invading pathogens
• an antibody is made by B lymphocytes and is a protein which binds to specific antigen found on the surface of specific bacteria or viruses, which then targets them for destruction
• an antitoxin is made by T lymphocytes and is a protein which binds to and counteracts toxins released by pathogens
• phagocytosis is when a pathogen is engulfed then destroyed by a phagocyte
• 1. lymphocytes produce antibodies which bind to pathogens, targeting them for destruction
• 2) lymphocytes produce antitoxins which counteract toxins produced by bacteria and immobilise the bacteria
• 3) phagocytes engulf and destroy bacteria by phagocytosis