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Preventing Disease Artificial immunity 2 of 38 © Boardworks Ltd 2008 Immunological memory What is vaccination? Vaccines stimulate the production of antibodies and memory cells against the target pathogen without causing illness. Why don’t vaccines cause illness? They may contain an inactivated form of the pathogen, killed by heat treatment (which leaves the immune-stimulating antigens intact). They may contain an attenuated (less virulent) form of the pathogen. They may contain isolated antigens, such as cell surface proteins, from the pathogen. 4 of 38 © Boardworks Ltd 2008 Influenza vaccines New strains of the influenza virus are constantly emerging. This is because antigens displayed on the virus change due to mutation. This causes antigenic variation. Antigenic variation makes it hard to immunize a patient against the influenza virus for life with just a single vaccine. The government works with other organizations to identify current strains of influenza. An effective vaccine is developed each year. 5 of 38 © Boardworks Ltd 2008 The MMR controversy In 1998, a scientific paper was published in the medical journal The Lancet, speculating that the MMR vaccine could cause autism. The authors thought that the MMR vaccine could damage the bowel, allowing toxins that are normally destroyed in digestion to move into the blood. If these toxins travelled to the brain they might cause autism. The authors did not prove that this was the case but still recommended that doctors stop administering the MMR vaccine until more research was done. 6 of 38 © Boardworks Ltd 2008 MMR: THE TRUTH BEHIND THE HEADLINES 1988 Measles, mumps and rubella vaccination introduced. 1996/7 Dr. Andrew Wakefield (and others) carried out research to establish whether or not there was a link between the MMR vaccine and autism. 1998 Paper published in The Lancet claiming that there was evidence for a link between the MMR vaccine, inflammatory bowel disease and autism. AUTISM “Autism is a lifelong developmental disability that affects how a person communicates with, and relates to, other people. It also affects how they make sense of the world around them.” The National Autistic Society MEASLES - Viral disease - Highly infectious - Transmitted via droplets - Complications include meningitis and pneumonia Case study MUMPS - Infectious viral disease - Transmitted via droplets - Complications caused when virus spreads from parotid glands to CSF RUBELLA - Infectious viral disease - Transmitted via droplets - Usually mild - Dangerous for unborn babies when mother is infected UK newspapers sensationalised the story, ignoring studies that refuted Wakefield’s claims. In April 2006, the first UK measles death for 14 years occurred. FINALLY… A journalist called Brian Deer started to look more closely at the situation… OUTCOMES • MMR is safe • Single vaccines less safe (lower uptake; more vaccines needed) • Wakefield struck off by GMC • Lives in US – anti-vaccination movement • Measles cases and deaths increased 25 of 38 © Boardworks Ltd 2008 Herd Immunity • If more people are vaccinated against a particular pathogen, an unvaccinated person is less likely to come into contact with someone who is carrying the pathogen. • This reduces the spread of disease. • Vaccination levels need to be high enough to protect everyone – HERD IMMUNITY. Herd Immunity • In order to protect a whole community against an infectious disease, at least 80% of the population need to be immunized. • This keeps the level of transmission low, protecting those who cannot be immunized. • The percentage needed to maintain herd immunity varies between different diseases; for example, the herd immunity threshold for measles is 83–94%. Past paper question Answers Answers Answers Answers cont’ What are monoclonal antibodies? Polyclonal antibodies are naturally produced in an immune response. Different plasma cells secrete antibodies, resulting in a variety of different antibodies against a specific antigen. Monoclonal antibodies (mAbs) are antibodies produced from clones of a single plasma cell and are therefore all identical. They have many important uses, such as: the treatment of cancer and other diseases drug screening home pregnancy kits scientific research. Production of monoclonal antibodies Large quantities of mAbs can be produced using mice or rabbits. A specific antigen is injected into the animal, stimulating the production of plasma cells. The plasma cells are removed from the animal and fused with cancerous myeloma cells from normal mice. These form immortal hybridoma cells, which can produce a single type of antibody indefinitely. Exam question – monoclonal antibodies Remember: - Antigen injected into animal - Plasma cells produced - Plasma cell fused with myeloma (cancer) cell - Hybridoma cell formed – multiplies quickly and indefinitely to produce many identical antibodies (for the original antigen).