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Transcript
Topics 6.3 & 11.1 The Boy in the Bubble David Vetter = born Sept 1971 His parents had a first son (also named David) that was born the year before, but died after 6 months because of SCID – severe combined immunodeficiency SCID – body is unable to produce wbc to fight off foreign invaders The disease is X linked, meaning that there is a 50% chance that a Vetter male child would have SCID When their second son David was born, he also had SCID and was placed in a “plastic bubble” 10 seconds after birth to keep him in a sterile environment away from foreign invaders. He lived in the bubble for 12 years Doctors hoped to cure him with a bone marrow transplant from his healthy sister. Unknown to doctors, Katherine had a virus in her marrow. When David received the transplant, the virus caused mononucleosis, and eventually grew out of control and lead to Burkitt’s lymphoma (a type of cancer) Knowing that he was dying, he spent his last few days of life outside the bubble. http://www.bing.com/videos/search?q=boy+in+the+bubble+disease&FORM=HDRSC3# view=detail&mid=4FD8CDA29BAB681AF9F44FD8CDA29BAB681AF9F4 Pathogen A pathogen is an organism or a virus that causes a disease in any other organism. Ie: Bacteria, fungi, viruses Exposure to the majority of pathogens does not result in a disease because We can prevent pathogens from entering our bodies We can develop an immunity to particular pathogens We can use chemicals (ie antibiotics) to defend ourselves. Viruses Non cellular structures Contain DNA or RNA surrounded by a protein coat. Not considered to be a living cell because they cannot undergo essential life process on their own (ie: replication or protein synthesis) (When a virus wants to replicate, it enters an (unwilling) “host” cell and uses the host’s enzymes to replicate its DNA. It takes away energy an resources from the host cell.) HPV EBOLA Polio Rabies Viruses and antigens Viruses will have antigens on its protein coat/cell membrane. All viruses must find a type of cell in the body that matches their own proteins in a complementary way so it can enter the cell (through endocytosis) This is why only certain body cells are damaged by certain viruses as is typically reflected in the symptoms associated with the infection. Bacteria Prokaryotic cells, that can rapidly duplicate A colony of bacteria can obstruct regular function in the host organism Bacteria products can cause unpleasant side-affects to a host organism. Streptococcus H. pylori Antibiotics Antibiotics are chemicals that may be used to fight off bacterial infections. Antibiotics often work by disrupting the ability of the bacterium from replicating and/or undergoing protein synthesis. (If they cannot undergo protein synthesis, they will lack the essential proteins for life – and thus die) (If they cannot replicate, the colony will not be able to increase in number and eventually the body’s immune system will be able to kill the remaining bacteria) Antibiotics Antibiotics do not disrupt cell function in your cells because bacteria cells are prokaryotic and you are made of eukaryotic cells. They are different enough that it doesn’t have an effect on your cells. Why can’t antibiotics be used to kill viruses? Viruses don’t undergo replication or protein synthesis on their own so there is nothing to disrupt. Antibiotics Antibiotics are often derivatives of fungus such as penicillin (which comes from the fungi Penicillium) Fungi Parasites 1st Line of Defense The first line of defense against foreign invaders is mainly physical The skin and the mucous membranes defend against viral and bacterial invaders. The skin provides a physical barrier like a wall preventing pathogens from getting in. The epidermal layer is constantly being replaced as underlying dermal cells die and are moved upwards. The epidermal layer is mainly dead cells and thus is a good barrier because it is of no use to viruses. Acidic secretions (pH 3-5) inhibit growth of microbes Mucous Membranes Weak points in our defense against foreign invaders are areas in which we are not protected by skin. Mucous membranes may help in these areas to trap micro- organisms and prevent further entry Examples…. In the trachea (which leads to the lungs), foreign particles are trapped in mucous or filtered by tiny hair-like structures called cilia that sweep particles to the entrance where coughs can expel them. Mucous Membranes In the stomach, corrosive acids and digestive enzymes destroy microbes that may be found in food. The vagina produces mucous and has an acidic environment too Lysozyme – an antimicrobial enzyme that is found in tears, saliva, mucous secretion, perspiration will destroy bacterial cell wall killing the bacteria. nd 2 line of Defense Kicks in when the invader takes up residence with in the body. INFECTION: the successful invasion of a pathogen Leukocytes are used to fight off an infection Leukocytes are white blood cells (wbc) Found in the blood stream but also in body tissues have a nucleus unlike rbc responsible for responding to foreign invaders and destroying them many different types Bone Marrow – where blood cells are made Carry O2 to cells Produce antibodies Find invaders and initiate attack Involved in blood clotting Macrophage Is a type of wbc that ingests foreign invaders by phagocytosis (Because it undergoes phagocytosis, it is also referred to as a phagocyte) All cells have proteins on their cell membranes called ANTIGENS Antigens act as identity markers. Macrophages recognize body cells of the host by its antigens Foreign invaders will have different cell surface antigens which will cue macrophages to get rid of them Phagocytosis This is the process when wbc ingest invading microbes and chemically destroy them with enzymes Macrophages –have pseudopods which are protrusions that will attach to the surface of an invading microbe, engulf it and digest it with enzymes This is a non-specific immune response because the identify of the pathogen is not determined (at this point) Animations http://www.pennmedicine.org/encyclopedia/em_Disp layAnimation.aspx?gcid=000098&ptid=17 Antibody Also known as an immunoglobulin Soluble proteins that are produced by the immune system as a response to the presence of an antigen Many different types Produced by different kinds of lymphocyte (each lymphocyte will recognize a particular kind of antigen and produce antibodies against that kind of antigen) Antibodies Attach themselves to antigens of foreign invaders. This will make the foreign invader useless and target it for phagocytosis HIV and the Immune System HIV: human immunodeficiency virus is a virus that infects the cells of the immune system It reduces the number of lymphocytes that are actively involved in the production of antibodies Leads to less antibodies which means the individual will be more likely to develop a disease. HIV Hard to find a cure or a vaccine. HIV hides in its host cell for years Mutates relatively quickly – always changing its antigens making it hard to vaccinate against and hard for body’s immune system to recognize it. AIDS HIV can lead to AIDS (aquired immune deficiency syndrome) In these cases, HIV has severely weakened the individual’s immune system and their lymphocyte count is particularly low. These individuals are susceptible to illnesses that healthy individuals have no problem fighting off such as the common cold AIDS transmission Through: Blood Semen Vaginal secretions Breast milk Most common transmission occurs via: Unprotected sex Sharing of injection needles Mother to child during birth or breastfeeding HIV animations http://highered.mheducation.com/sites/0072943696/ student_view0/chapter14/animation__hiv_replication. html http://highered.mheducation.com/sites/0072943696/ student_view0/chapter14/animation__how_the_hiv_i nfection_cycle_works.html Social Implications of AIDS In 2006, more than 60% of people living with HIV/AIDS were from Sub-Sahara Africa. Of the 3 million people who died from AIDS related diseases in 2006, 2 millions of them were from SubSaharan Africa The number of new infections in North America and Western Europe have either stayed the same or decreased. This is believed to be the result of HIV prevention programs and education Lack of these programs in Sub-Saharan African is likely the reason why HIV/AIDS is not declining in this areas Social Implications People with HIV/AIDS can suffer from stigmas and discrimination Women are more likely to contract HIV from sex with an infected partner than men. People who die from HIV/AIDS are often at an age where thery are the most productive members of society – removing individuals from the work force and delaying economic growth, an creating orphans Social Implications Unemployment poverty cannot afford treatments Poverty increases the chances of contracting HIV/AIDS due to lack of education on safe sex and increased prostitution Neutrophils – attracted to chemical signals given off by wbc damaged by microbes. They migrate toward infected tissue and engulf the microbe and wbc This creates pus – which is fragments of proteins and dead wbc and the digested microbe. When tissue is damaged because of physical injury the body responds with localized inflammatory response: swelling, heat, redness, pain If pus is present too, its a sign that the second line of defense has been at work Fever – this is the body’s response to infection When chemicals released by wbc reach the hypothalamus relaying information that the body is fighting off an infection, the hypothalamus’ response is to raise body temperature to ~40°C These conditions make it harder for the invader to survive and reproduce Some believe taking meds to reduce fever may prolong infection But high temperatures can be dangerous to humans who’s cells can’t survive above 43°C