Defence Against Disease Noadswood Science, 2011

Defence Against Disease Saturday, May 12, 2018 To understand how the body defends itself against disease

Pathogen Barriers Complete the pathogen barriers worksheet

Pathogen Barriers Wax traps micro-organisms Tears contain an enzyme which kills micro-organisms Hairs and mucus stop micro-organisms from entering the body Saliva contains an enzyme which kills micro-organisms Blood contains white blood cells which kill any micro-organisms within the body Skin barrier stops micro-organisms from entering the body

Defence How does our body defend us from micro-organisms? The breathing organs produce mucus to cover the lining of these organs and trap the microbes The skin acts as a barrier If our skin is cut platelets seal the wound by clotting Our blood contains white blood cells

Passive & Active Defence The body has different ways of protecting itself against pathogens The first defence is passive immunity – aimed at stopping the pathogen getting into the body in the first place The body’s passive immunity system includes: - Skin Mucus and cilia (tiny hairs) in the respiratory system Acid in the stomach Enzymes in tears If a pathogen still manages to get into the body, the second defence takes over – this is called active immunity, and the white blood cells have key functions in this…

Bacterial Investigation Complete the bacterial investigation…

White Blood Cells White blood cells can: - Ingest pathogens and destroy them Produce antibodies to destroy pathogens Produce antitoxins that neutralise the toxins released by pathogens Pathogens are not the disease – they cause the disease! White blood cells ingest pathogens (they do not eat them!)

White Blood Cells There are several different types of white blood cells, each with different functions, but they can be put into two main groups: - Phagocytes or macrophages Lymphocytes

Phagocytes Phagocytes can easily pass through blood vessel walls into the surrounding tissue and move towards pathogens or toxins They then either ingest and absorb the pathogens or toxin; or release an enzyme to destroy them Having absorbed a pathogen, the phagocytes may also send out chemical messages that help nearby lymphocytes to identify the type of antibody needed to neutralise them

Phagocytes

Lymphocytes Pathogens contain certain chemicals that are foreign to the body and are called antigens Each lymphocyte carries a specific type of antibody - a protein that has a chemical 'fit' to a certain antigen When a lymphocyte with the appropriate antibody meets the antigen, the lymphocyte reproduces quickly, and makes many copies of the antibody that neutralises the pathogen Pathogen (coated in antigens) Antibodies attach White blood cell

Lymphocytes

Antibodies Antibodies neutralise pathogens in a number of ways: - They bind to pathogens and damage or destroy them They coat pathogens, clumping them together so that they are easily ingested by phagocytes They bind to the pathogens and release chemical signals to attract more phagocytes Lymphocytes may also release antitoxins that stick to the appropriate toxin stopping it damaging the body

Antibodies Step 1 – the white blood cell identifies the pathogen Step 2 – antibodies produced to ‘fit’ the pathogen Step 3 – antibodies fit the pathogen, ‘clumping’ them Step 4 – the white blood cell ingests the pathogen

Antibodies

Fighting Diseases Natural immunity – antibodies are produced by a person when needed or they are passed on by the mother during pregnancy Artificial immunity – a vaccine with dead microbes is injected tricking the body into producing antibodies ready for the real thing

Vaccinations & Immunisation Vaccination – taking a vaccine as a precaution against a disease Immunisation – making an animal resistant (immune) to a disease by taking a vaccine

Vaccination People can be immunised against a pathogen through vaccination Vaccination involves putting a small amount of an inactive form of a pathogen, or dead pathogen, into the body Vaccines can contain: - Live pathogens (treated to make them harmless) Harmless fragments of the pathogen Toxins produced by pathogens Dead pathogens These all act as antigens – when injected into the body, they stimulate white blood cells to produce antibodies against the pathogen

Vaccination Because the vaccine contains only a weakened or harmless version of a pathogen, the vaccinated person is not in danger of developing disease - although some people may suffer a mild reaction If the person does get infected by the pathogen later, the required lymphocytes are able to reproduce rapidly and destroy it

Boosters Vaccines in early childhood can give protection against many serious diseases Sometimes more than one vaccine is given at a time, like the MMR triple vaccine against mumps, measles and rubella Sometimes vaccine boosters are needed, because the immune response 'memory' weakens over time (anti-tetanus injections may need to be repeated every ten years)

Vaccine Example Complete a cartoon strip to show how a vaccine works… The discuss the pros / cons of vaccines within your groups

Vaccine A preparation of dead or weakened pathogens, that is used to induce formation of antibodies or immunity against the pathogen Real pathogen for disease Vaccine for disease ( a weakened version)

Vaccine Vaccine (pathogen) injected into the bloodstream Injection

Vaccine Vaccine enters the blood stream skin White blood cells Vaccine (pathogen) Blood vessel Red blood cells

Vaccine White blood cells detect a foreign body and surround it

Vaccine White blood cells make antibody against the vaccine (pathogen) Antibody – this is specific to this particular vaccine (pathogen)

Vaccine The antibody acts as a marker for other white blood cells to come along and engulf the vaccine (pathogen) White blood cells that destroy pathogens

Vaccine The vaccine (pathogen) has been destroyed and the antibody is left in the blood stream (active immunity) *In passive immunity the body is actually given the antibodies – this only lasts at most a few years

Vaccine Pros & Cons Pros Cons Protection against disease Some side effects, e.g. bruising Protection against more serious damage e.g. brain damage and death Discomfort for young children Reduces chances of an epidemic Some health concerns (MMR and autism link (dismissed)) It is cheaper to give a vaccine than treat an infected patient Reduces hospital load MMR is 3 immunisations in 1

MMR Controversy Research the measles, mumps rubella (MMR) vaccination controversy – was there any scientifically significant link between the MMR jab and autism… How did Andrew Wakefield collect the data, and should he have conducted the study? Was 12 individuals enough to warrant the study? How should he have collected the data, and how much data should he have taken? What long term problems has this study caused?