Diseases and immunity

Slide 1

• Pathogen: a disease-causing organism.
• Antibodies lock onto antigens (proteins that are found on the surface of the pathogen), leading to the direct destruction of pathogens or marking of pathogens for destruction by phagocytes.
• Each pathogen has its own antigens, which have specific shapes. This means that specific antibodies which fit the specific shapes of the antigens are needed.
• Transmissible disease: a disease in which the pathogen can be passed on from one host to another.
• The pathogen for a transmissible disease may be transmitted either through direct contact, e.g. bodily fluids, or indirectly e.g. contaminated surfaces.
• Active immunity: defense against a pathogen by antibody production in the body.
• Active immunity is gained after an infection by a pathogen, as the body knows which antibodies to produce to destroy the pathogen, or by vaccination.
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Bodily defenses

• Mechanical barriers: Skin, hairs in the nose.
• Chemical barriers: Mucus and stomach acid.
• Cells: Phagocytes and antibody production by white blood cells.
• These defenses can be enhanced by vaccination.
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Vaccination

• A harmless pathogen with antigens is injected into the blood of the person.
• The antigens trigger an immune response by lymphocytes (which produce antibodies).
• Memory cells are produced that give long-term immunity.
• Vaccines help control the spread of diseases as once a person has been vaccinated their body is able to produce the antibodies to destroy the antigens and therefore the risk of the disease being transmitted is lowered.

Controlling the spread of disease

• Certain methods can be used to control the spread of disease, such as:
• Hygienic food preparation
• Good personal hygiene
• Waste disposal
• Sewage treatment
• These are important as they help to kill bacteria on surfaces to prevent cross-contamination and transmission between people, such as shaking hands with someone.
• Methods like waste disposal and sewage treatment also help to prevent pathogens from reentering our system due to the lack of exposure and proper disposal.

Passive immunity

• Passive immunity: short-term defense against a pathogen by antibodies acquired from another individual, e.g. mother to infant.
• Memory cells are not produced in passive immunity.
• Importance of passive immunity for breast-fed infants:
• Less likely to develop certain diseases -> less risk of death.
• Helps the baby's immune system grow stronger.
• Some diseases are caused by the immune system targeting and destroying body cells, such as Type 1 diabetes.