Disease and the Immune System PDF

Disease and the Immune System A high-resolution time-lapse of an immune cell (red) hunting down and destroying cancerous tumour cell (blue) Learning intentions: Diseases Understand the difference between infectious and non-infectious diseases Describe how humans become infected with patho...

Disease and the Immune System A high-resolution time-lapse of an immune cell (red) hunting down and destroying cancerous tumour cell (blue) Learning intentions: Diseases Understand the difference between infectious and non-infectious diseases Describe how humans become infected with pathogens (methods of infection) Recognize that infectious diseases can be caused by different organisms or agents such as bacteria, fungi, and viruses.  What is a Disease? Discuss with the person next to you and write your own definition of the word DISEASE. Can you name 5 diseases?  What is a Disease? Disease is any condition in which the body or parts of the body do not function properly. Melanoma (skin cancer) Tonsillitis Chickenpox (Sore throat) Rheumatoid arthritis  Classifying Diseases Diseases can be classified into groups based on how a disease is obtained. Sometimes referred to as ‘Contagious’ if the disease spreads from one person to another person ie. COVID-19 Diseases that are infectious but not contagious ie. ear infectious and Diseases Lyme disease. Congenital Diseases Acquired Diseases Ageing (arthritis, heart Cancer (stomach, Communicable/ infectious Non-communicable/ disease) breast, colon) diseases non-infectious diseases Chemical/metabolic Nutritional Mental (depression, (lactose intolerance, schizophrenia) (anaemia, diabetes) Cellular Non-cellular osteoporosis, Environmental pathogens pathogens obesity) (drug-related, Inherited (haemophilia, accident- colour blindness, cystic related, fibrosis) Bacteria (botulism, Viruses (influenza, tetanus, tuberculosis, Fungi (thrush, tinea, asbestos- ringworm) measles, AIDs, Prions (bovine spongiform cholera) chickenpox, COVID- encephalopathy – mad cow related) 19) disease) Protozoa (malaria, Animals (louse, liver giardiasis) fluke, tapeworm)  Non-Infectious Non-infectious diseases not caused by pathogens, may be caused by such things as lifestyle factors, environmental toxins, or gene inheritance or mutations. Examples include: Diabetes Cancer Epilepsy Asthma and Allergies Allergy Diabetes  Infectious diseases Infectious diseases are caused by pathogens and can spread from one organism to another. Pathogens are disease causing organisms. Pathogens can be: Cellular (made out of cells) ie. Bacteria and fungi Non-cellular (not made of cells) ie. Viruses and prions ‘Achooooo’ The symptoms of infection with the pathogen are what causes the disease. The worse the symptoms, the higher the virulence. Virulence is the severity or harmfulness Allergy Diabetes of a disease or poison. How do infectious diseases spread? an organism that helps transmit infection from one host to another (often does not show any symptoms of the disease) ie. mice/rats, fleas, mosquitoes/flies. Contact with infected person or animal How the Bubonic Plague was transmitted Example, when a Flea serves as the vector to infect humans with Bubonic Plague (caused by bacteria). The flea acquires the bacteria from rats when it takes a blood meal. If the same flea subsequently feeds on a human (host), the plague bacteria can be transferred, and the result can be bubonic plague in humans. Learning intentions: Pathogens Viruses: Recount how viruses are non-cellular agents (non-living) and need to replicate in a host cell. Outline how good hygiene and social practices can help stop the spread of disease Bacteria Bacteria are small single-celled organisms that can come in good (beneficial) forms and bad (pathogenic) forms that cause disease.  Bacterial diseases - examples Diptheria Lyme Disease Meningitis  Fungi A KINGDOM of organisms that have a cell wall made of CHITIN. Fungi live in air, in soil, on plants and in water. Fungi reproduce asexually by fragmentation, budding, or by producing spores. You can inhale the spores or they can land on you. As a result, fungal infections often start in the lungs or on the skin. Parasitic fungi use enzymes to break down living tissue, which causes illness in the host.  Fungal diseases - examples Thrush Ringworm Tinea/Athlete’s Foot Viruses A virus is a tiny, infectious particle that can reproduce only inside a host cell. Viruses "commandeer" the host cell and use its resources to make more viruses, basically reprogramming it to become a virus factory. Because they can't reproduce by themselves (without a host), viruses are not considered living. COVID-19 is a serious infectious disease caused by a pathogenic and new strain of coronavirus. ANTIBIOTICS DO NOT WORK AGAINST VIRUSES Virus structure However, they have the following Viruses are structurally diverse. features in common: A protective protein shell, or capsid DNA tucked inside of the capsid Capsid enables the virus to attach to the host cell Virus reproduction 1. Virus injects DNA into the host cell. 2. Viral DNA is replicated by the host cell’s organelles. 3. 1000s of new viruses burst the cell to go on and infect 1000s of new host cells. Viral Diseases Polio Rabies Hepatitis Rubella COVID-19  How do we stop the spread of disease? What strategies are used depends on the pathogen and its mode of transmission. These include: Vaccination programs Strategies to help authorities assess risk, eg contract tracing, testing, wastewater testing Strategies that restrict movement, eg lockdowns, quarantining, isolating Strategies that reduce spread, eg masks, social distancing, washing hands. Treatment with antibiotics (only bacteria) and antivirals Social strategies are implemented to support scientific strategies, and include: public awareness campaigns, funding for vaccine research and roll out, public compliance/enforcement, international cooperation. Learning intentions: The Immune System Define and give examples of the First line of defence (passive immune system). Define and give examples of the Second line of defence, and the immune cells involved. Define and give examples of immune cells involved in the Third line of defence. Understand and explain the function of B and T cells. Explain the function of antibodies in the body.  The onset of disease Pathogens can enter the body in a number of ways: Through Food and Water Breathing In Cuts and Wounds Once infected, depending on the disease, it may only take a few days before any symptoms appear. This time is called the incubation period. An incubation period occurs because the pathogen needs to multiply and toxins often need to build up. Your body has THREE Lines Of Defence against Disease Ctrl + click on the image to watch the videos. The First Line of Defence Pathogens can enter the body in many ways. The body’s first line of defence is designed to stop them from entering the body. These defences can be: Physical barriers – such as intact skin, cilia and nasal hairs. Chemical barriers — body fluids such as saliva, tears, and stomach acid. Biological – good bacteria in on our skin and the lining of our intestine that prevents bad bacteria from flourishing. They do this by out competing the harmful bacteria for food and space.  The First Line of Defence Barriers are chemical or physical: Barrier Chemical Physical Skin (+ acid on x x skin) Tears x Stomach acid x Mucus x Saliva x Cilia (hair-like X structures) in the throat Nose hairs x The Second Line of Defence Once pathogens enter the body, the second line of defence gets started. This includes: Clip 1. Inflammation White blood immune cells called ‘Mast Cells’ release HISTAMINE, a chemical that causes an INCREASE of blood flow to the area where pathogens have been detected. White blood cells then come in and consume pathogens (Phagocytosis) – next slide This leads to the site becoming RED, SWOLLEN, HOT and PAINFUL. 2. Fever: having a high fever may be uncomfortable, but it is an important part of the immune response, as a rise in temperature will make it harder for the pathogens to survive. 3. Blood clots (and then scabs), prevent pathogens from entering the blood. 4…. Next slide *drum roll*  4. Phagocytes Phagocytes are a type of immune cells involved in the second line of defence. E.g. Macrophages, Neutrophils and Monocytes. Macrophages ingest and absorb the pathogens that invade the body through a process of Phagocytosis. In theory… Having digested a pathogen, the macrophage then is able to present the pathogenic antigen (part of the pathogen) to a Lymphocyte (T helper cell – third line immune cell) in order to initiate the third line of defence. What happens in reality… Non-specific immune response The first and second lines of defence are innate – this means that they are present at birth. They are not specific – this means that they defend against infection in a way that is the same for any invading pathogen. Non-specific immunity provides an instant response to an invading pathogen. Third Line of Defence – specific immunity. The 3rd line of defence is carried out by specialised white blood cells called Lymphocytes. There are two types: T cells and B cells. What’s so special about third line of defence? Is Specific – it differentiates between specific pathogens. Is Acquired – it depends on the types of pathogens that the body is exposed to from the time of birth to death. There is an immunological memory (Memory B cells). This means that a particular pathogen will be recognised by the body’s immune system upon secondary exposure to this pathogen and that the immune response will be greater and more rapid the second time round, such that the pathogen is completely eliminated before it has the ability to cause disease. This is the basis from which vaccines have been developed by scientists, for particular diseases. A major component of specific immunity is the production of specific antibodies against specific pathogens by B cells. B cell producing antibodies.. Antigens Pathogens contain chemicals that are foreign to the body called antigens. They are the unique “shape” present on the surface of a pathogen. Our immune system uses these to determine what is “Self” and what is “non-self” (foreign). T Cell Lymphocytes Some T-cells find and destroy infected cells. Like B-cells, they attack only one kind of pathogen, by recognising its unique antigen on the surface of the infected cell. They attach to the outside of the cell and secrete chemicals into the cell that destroys it. In theory… In reality… B Cell Lymphocytes B-cells (Plasma cells) produce antibodies - proteins that have a chemical 'fit' to a specific antigen in a complementary manner. This means that antibodies are designed to attack only one kind of antigen. For example, an antibody designed to destroy smallpox is unable to attack the common cold. The enormous diversity of antibodies allows When a B-cell with the matching antibody meets the immune system to recognize an equally the antigen, it makes many copies of the antibody, wide variety of antigens (pathogens) which neutralise the pathogen. How is the third line of defence involved? Cell-mediated immunity It all starts when a Macrophage (2 nd line of defence cell) digests a pathogen, it presents the pathogenetic antigen to a T-helper cell. T-helper cell then creates copies of itself (clonal expansion) Some of these copies differentiate (specialise) into Cytotoxic T- cells, and others into Memory T-cells. Cytotoxic t-cells not only attack foreign invading cells, but may also attack your own cells that have been infected or are cancerous. How is the third line of defence involved? Humoral immunity T-helper cells also secrete Cytokines to activate B- Cells. Activated B-Cells then create many copies of themselves (clonal expansion), then differentiate into Memory B-Cells and Plasma Cells. These plasma cells produce proteins called antibodies that are specific to the invader’s antigens. These antibodies assist in the destruction of the invading pathogen. B memory cells and T memory cells formed during the adaptive immune response remain in the blood for an extended period of time, allowing the body to respond to pathogens it has previously encountered quickly and effectively.  How do Antibodies neutralise pathogens? …in a number of ways: 1. They can bind to pathogens and damage or destroy them. 2. They can coat pathogens, clumping them together so that they are easily ingested by phagocytes (2nd line). 3. They can bind to the pathogens and release chemical signals to attract more phagocytes (2nd line). Long lasting Immunity Most T cells and B cells die after the infection has been brought under control. Some remain for many years. These are called MEMORY T and B CELLS. If you become infected again with the same pathogen, the memory cells respond much FASTER and STRONGER compared to the first encounter with the pathogen. The pathogen is destroyed much more quickly. This is what is meant when we say “we are immune” and why we can’t get the same disease twice. Learning intentions: Vaccines and Antibiotics List and explain the types of vaccines including dead pathogens, weakened strains and parts of broken-down pathogens. Explain the concept of herd immunity and the importance of vaccinations. Understand that antibiotics are only used for bacterial infections Understand why antibiotic resistance occurs in society Vaccines People can be immunised against a pathogen through vaccination. Different vaccines are needed for different pathogens. 26 doses of 9 vaccines Vaccinations in early childhood protect against many serious by the first birthday diseases. Sometimes more than one vaccine is given at a time, 48 doses of 14 like the MMR triple vaccine against mumps, measles and vaccines by age 6 and rubella. a total of 70 doses of 16 vaccines by age 18 The vaccine contains a weakened or harmless version of a pathogen, which means that the vaccinated person is in no danger of developing the disease. The challenge in 2020, was for a COVID-19 vaccine to be developed, trialled and distributed. How do Vaccines work? Looking at the graph… 1st injection: produces immune response (antibodies). 2nd injection: memory B and T cells ensure quicker response if the pathogen is encountered later. Protective antibody level is reached and only and annual booster is needed after that. The vaccine conditions the immune system to respond however it poses no real threat to the body. Upon exposure to an actual pathogen, a secondary fast and strong response is elicited. History of Vaccination Edward Jenner and the Cowpox vaccination Clip  Herd Immunity If enough people in a community are immunised against an infectious disease, it is harder for the disease to spread. Protection of “the herd” is achieved when immunity reaches a certain value, which is different for each disease. Watch this video: Herd immunity is important because there are members within every community who are not immune/cannot be vaccinated, such as the elderly, Australians are not at herd immunity levels for newborn babies and people being treated for cancer. any of the vaccinations in the National immunisation program! Antibiotics Antibiotics are drugs that are used to treat bacterial infections only. They are not effective against viruses, such as the common cold or flu. Nor are they effective for treating COVID-19, which is also caused by a virus. In 1928, Alexander Fleming noted that mould belonging to the genus Penicillium produced a chemical that stopped the growth of bacteria. Fleming called this unknown antibacterial substance penicillin. Penicillin has saved more than 200 million lives. Antibiotic resistance Overusing antibiotics is a major cause of antibiotic resistance. Overuse has created superbugs – strains of bacteria that have adapted after coming into contact with an antibiotic. Once this happens, these bacteria become "resistant" to the antibiotic to which they have been exposed, which means the antibiotic cannot kill the bacteria or stop them from multiplying. The World Health Organisation has identified antibiotic resistance as one of the greatest threats to human health. https://www.sbs.com.au/news/doctors-warn-about-superbugs-antibiotic- resistance-in-australia Measures to reduce antibiotic resistance Do not take antibiotics for non-bacterial infections Take the full prescription even if you are feeling better. Never share antibiotics with others or use leftover prescriptions.