Immunology Project - by Nicola Heath

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1 Part A - Pathogens Immunology Project - by Nicola Heath Pathogens are a biological agent that causes disease or illness to its host. We come in contact with pathogens everyday. Most of the time our body s immune system destroys them before they can cause harm. We are considered exposed when we have been in contact with a pathogen. We are considered infected when a pathogen has entered the body and resulted in disease. The major categories of Pathogens: Prions - non cellular An infectious protein that causes the degeneration of brain tissue in mammals. They occur mainly in nerve cells and convert normal protein to prison protein. They spread by eventually bursting and infecting other cells, prions are around 10nm in size. Examples of Prion infections are BSE (Bovine Spongiform Encephalitis) - Mad Cow Disease. Viruses - non cellular A ultramicroscopic incurious agent that replicates itself only within cells of living hosts. They are pieces of nucleic acid (DNA or RNA) wrapped in a thin coat or protein. Reproduce and result in the death of other cells and are around nm in size. Examples of viruses diseases are influenza, AIDS or chicken pox. Bacteria - cellular Prokaryotic cells that are present in the soil, air, water, and in many human body parts (eg skin). They produce toxins often as waste products, which harm the host. Bacteria reproduces by binary fission so that within a short time the host can contain thousands of bacteria. They are around 1-5um in size. Examples of bacteria virus are tetanus, tuberculosis, pneumonia and whooping cough. Fungi - cellular Eukaryotic organisms composed of a system microscopic tubular filaments or threads. They branch to form a mycelium structure. Fungi produce fruiting bodies which contain thousands of spores by which the fungi reproduces. They play an important role in decomposition of organic material. Examples of fungi are candidacies (thrush), tinea (athletes foot) or ringworm in humans. Top 10 Infectious Disease Killers 1) Whooping Cough 2) Mumps 3) Tuberculosis 4) Diphtheria

2 5) Polio 6) Smallpox 7) Dengue Fever 8) HIV 9) Ebola 10)Typhoid A map to show the outbreak of viral disease - mumps (the dark reddish colour). A map to show the outbreak of bacterial disease - Tuberculosis. Part B - Immune System The immune system is the body's defence system against infectious organisms and other invaders. It is made up of a network of cells, tissues and organs that work to protect the body. White blood cells (leukocytes) seek out and destroy disease causing organisms or substances. They are made in the bone marrow. There are two main types of leukocytes: granulocytes and agranulocytes. Granulocytes have granular cytoplasm and a lobed nucleus. Agranulocytes have smooth cytoplasm and a nonlobed nucleus.

3 The immune system has 3 lines of defence to defend the body from diseases. The first line of defence : Chemical and Physical barriers Physical barriers include the skin and the mucous membranes of the airways, guts, urinary and reproductive systems. Chemical barriers include hydrochloric acid secreted by the stomach lining. Pathogenic microorganisms must make it past this first line of defence. If this defence is broken, the second line of defence within your body is activated. The second line of defence: Responses There are 4 main ways the body sends responses to fight off diseases: 1) Inflammation Invading microorganisms trigger inflammation. Inflammation involves an increase in blood flow to the affected part of the body, which leads to swelling, pain and an increase in temperature. Mast cells and Basophil are involved in inflammation. 2) Phagocytosis White blood cells engulf microbes or cells that are infected, damaged or dying. They enclose the particle or cell with a phagosome and then break down the contents with hydrolytic enzymes. Some cells then become antigen-presenting cells which present the digested remains to other immune cells. 3) Complement Around 30 proteins in the blood plasma that can be activated by the presence of microbes or antigen complexes. Complement can destroy pathogens and activate phagocytic cells. 4) Natural Killer (NK) cells NK cells kill pathogen-infected cells and cancer cells. They also release chemicals called cytokines, which alert and attract other immune cells. The third line of defence: Specific Immune System (adaptive)

4 In vertebrates it provides long lasting protection against specific pathogens or foreign substances. This system relies on antigens, which are specific substances found in foreign microbes. There are certain steps that are taken in the immune response: 1) When an antigen is detected by a macrophage, this causes T-cells to be activated. 2) The T-cells secrete interleukin 2. Interleukin 2 causes the rapid increase of certain cytotoxic T-cells and B-cells. 3) From here, the immune system follows two paths. One following T-cells and one following B-cells. As seen in the diagram below the three lines of defence work in a structured way to fight diseases. Cytotoxic T-Cells: Cytotoxic T-Cells are capable of recognising antigens on the surface of infected body cells. The cytotoxic T cells bind to the infected cells and secrete cytotoxins that induce apoptosis in the infected cell and perforins that cause perforations in the infected cells. Both of these mechanisms destroys the pathogen in the infected body cell. T Cell Pathway: T-cells can either directly destroy the microbes or use chemical secretions to destroy them. At the same time, T cells stimulate B cells to divide, forming plasma cells that are able to produce antibodies and memory B cells. If the same antigen enters the body later, the memory B cells divide to make more plasma cells and memory cells that can protect against future attacks by the same antigen. When the T cells stimulate the B cells to divide into plasma cells, this is called antibodymediated immunity. This is shown in the diagram below.

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6 Infectious Disease in Australia - Whooping Cough Fact Sheet The Basic Facts: Also called Pertussis A severe cough Caused by the bacterium Bordetella pertussis Immunisation is the best way to reduce the cough The Pathogen that causes whooping cough is a bacterium called Bordetella pertussis. These bacteria attach to the cilia that line part of the upper respiratory system. Now in developed countries, people who are most likely to develop whooping cough are: Newborns until they have their primary vaccinations. Children who have not been immunised. People whose last immunisation was over a decade ago. Children are also most at risk of developing more serious symptoms. This is because they can be much more life threatening. Whooping Cough is a serious, contagious, respiratory infection. The disease begins as a cold, which later develops into the cough. Whooping cough can last up to three months - even after treatment or no longer being infectious. The symptoms of whooping cough begin with the common cold and can then develop into: Severe cough - which occurs in short episodes 'whooping' sound on inhalation vomiting at the end of coughing apnoea - the child stops breathing at the end of coughing and can go blue The symptoms can be associated with poor appetite, fatigue and dehydration. The diagnosis for whooping cough can be found by using: Medical history using immunisation status Physical examination Blood tests Swabs of the nose and throws for testing But these tests are not always reliable and can take a lot of time. The treatments available for whooping cough are antibiotics, if the treatments is given within the first 21 days of contracting disease it can risk the likelihood of passing the infection to someone. The other treatment against whooping cough is vaccinations. Vaccinations are taken at a number of stages in a lifespan to increase immunisation from the disease. Diagram 1) A labelled diagram of the bacterium - Bordetella Pertussis - which causes whooping cough

7 Infectious Disease in China - Typhoid Fever Fact Sheet The Basic Facts: A bacterial infection of the intestinal tract and bloodstream Typhoid and paratyphoid fevers can be fatal The bacterium responsible for typhoid is called Salmonella typhi The bacterium is carried only by humans Typhoid Fever is a bacterial infection of the intestinal tract and bloodstream. Typhoid Fever is more common in places with unsafe water supplies and poor sanitation. It is transmitted by the spread of bacteria from faeces and urine and poor sanitation, or through poor water source. The symptoms of Typhoid Fever can last for a month and may include: Fever Fatigue Sore throat and coughing Headache Slower heart rate Sweating Abdominal pains Changes in bowel patterns Rash Mental changes Blood poisoning Enlarged Spleen Enlarged Liver The Pathogen that causes Typhoid Fever is a bacterium called Salmonella paratyphi. These bacteria are carried by humans. People who are most likely to develop Typhoid Fever are: People who have not been immunised. People in countries or areas with low standards of hygiene and water supply facilities. People travelling to these countries. These countries include: India, Pakistan and Bangladesh most countries of South-East Asia Papua New Guinea Central and South America the Caribbean African countries countries of the Middle East. The diagnosis for Typhoid Fever can be found by using: Physical examination Medical and Travel History Blood Test Faeces or urine tests Bone marrow tests The treatments available for Typhoid Fever are: Hospitalisation Antibiotics - to kill bacteria Plenty of fluids - to counter the dehydration caused by diarrhoea and fever The other treatment against Typhoid Fever is vaccinations. Vaccinations are combined with hepatitis. They are not 100% effective as about 20-50% of vaccinated people still contract the disease. It is recommended to be vaccinated 2 weeks before travelling to a county with a high risk of Typhoid Fever. Diagram 1) A labelled diagram of the bacterium - Salmonella Paratyphi - which causes Typhoid Fever These symptoms can range from mild to severe.

8 Part E - Vaccines Vaccines help prepare the body to fight off disease without exposing it to the disease symptoms. Vaccines are made of dead or weakened antigens. They can't cause an infection, but the immune system still sees them as an enemy and produces antibodies in response. Vaccines help develop immunity by imitating an infection. This type of infection does not cause illness, but it does cause the immune system to produce T- lymphocytes and antibodies. Sometimes, after getting a vaccine, the imitation infection can cause minor symptoms, such as fever. These minor symptoms are normal helps the body build immunity. Once the imitation goes away the body is left with a supply of 'memory' lymphocytes which help the body remember how to fight the disease in the future. To prevent Typhoid Fever there are two main vaccines: one is an inactivated vaccine taken as a shot (Vi vaccine) and the other is an active but weak vaccine taken orally (Ty21a). Vi Vaccine is taken in a single dose whereas Ty21a is given in 3-4 doses and is taken around 2 days apart. The Typhoid Vaccine is not always 100% effective and care should still be taken when eating and drinking. Large scale clinical trials in China found that the Vi Vaccine granted 70% protection for at least 3 years. It was also found that the Ty21a Vaccine granted 53-78% protection for at least 5 years. This shows that even though there is protection against Typhoid in China it isn't always going to be the best method of protection. Bibliography ACC. (n.d.). Immune System. Retrieved from Inflammatoryresponse.html. Better Health Channel. (n.d.). Typhoid and Paratyphoid. Retrieved from Better Health Channel. (n.d.). Whooping Cough. Retrieved from BigPicture. (n.d.). The Immune Response. Retrieved from yr9science/files/2012/05/bp-immune-response-poster_col.pdf. Matthews, D. (2014). The world's deadliest and most infectious diseases, in one chart. Retrieved from Search For Better Health. (n.d.). Types of Pathogens. Retrieved from searchforbetterhealth.wikispaces.com/types+of+pathogens. The Travel Doctor. (n.d.). China. Retrieved from File/fact-sheets/9115%20TD%20Health%20Fact%20Sheet%20China.pdf. World Health Organisation. (n.d.). Background Paper on Vaccination against Typhoid Fever using New-Generation Vaccines. Retrieved from SAGE_Background_paper_typhoid_newVaccines.pdf. CDC. (n.d.). Typhoid Vaccines. Retrieved from CDC. (n.d.). Typhoid Vaccines. Retrieved from