Diseases and immunity

• Pathogen


  A microorganism that can cause diseases
• Transmission


  Passing a pathogen to an uninfected person
• Transmissible diseases


  A disease in which the pathogen can be passed from one host to another
• Vector


  An organism that carries a pathogen from one host to another
• Immune system


  The body's internal defence system
• Immune


  Able to fight off a particular pathogen before it causes any symptoms in the body
• Phagocytes


  White blood cells that surround, engulf and digest pathogens
• Lymphocytes


  White blood cells that produce and release antibodies
• Memory cells


  Cells produced by active lymphocytes that remain in the body and are able to respond quickly to a pathogen
• Antigens


  Chemicals on the surfaces of pathogens which are recognised as foreign by the body
• Antibodies


  Chemicals secreted by lymphocytes which attach to antigens and help to destroy them
• Antibiotic


  A drug that kills bacteria in the human body without killing human cells
• Penicillin


  An antibiotic which destroys bacteria by damaging their cell walls
• Auto-immune disease


  A disease caused by a person's own immune system attacking parts of their body
• Vaccination


  Introduction to the body of dead or weakened pathogens to make a person immune to an infectious disease
• Active immunity


  Defence against a pathogen by antibody production
• Passive immunity


  Short term defence against a pathogen by antibodies acquired from another individual