10. Diseases and Immunity

• Define pathogen as a disease-causing organism

• Define transmissible disease as a disease in which the pathogen can be passed from one host to another

• State that the pathogen for a transmissible disease may be transmitted either through direct contact, e.g. through blood or other body fluids, or indirectly, e.g. from contaminated surfaces or food, from animals, or from the air

• State that the body has defences:

– mechanical barriers, limited to skin and hairs in the nose

– chemical barriers, limited to mucus and stomach acid

– cells, limited to phagocytosis and antibody production by white blood cells

– which can be enhanced by vaccination

• Explain the importance of hygienic food preparation, good personal hygiene, waste disposal and sewage treatment in controlling the spread of disease

• State that antibodies lock on to antigens leading to direct destruction of pathogens, or marking of pathogens for destruction by phagocytes

• Explain how each pathogen has its own antigens, which have specific shapes, so specific antibodies which fit the specific shapes of the antigens are needed

• Define active immunity as defence against a pathogen by antibody production in the body

• Explain that active immunity is gained after an infection by a pathogen, or by vaccination

• Explain the process of vaccination:

– harmless pathogen given which has antigens

– antigens trigger an immune response by lymphocytes which produce antibodies

– memory cells are produced that give long-term immunity

• Explain the role of vaccination in controlling the spread of diseases

• Explain that passive immunity is short-term defence against a pathogen by antibodies acquired from another individual, e.g. mother to infant

• State that memory cells are not produced in passive immunity

• Explain the importance of passive immunity for breast-fed infants

• State that some diseases are caused by the immune system targeting and destroying body cells, limited to type 1 diabetes