Jen Parks - Topic 12
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Topic 12
12.1 Agents that Cause Infectious Disease
12.1.1 Pathogen- Organism causing disease
12.1.2 Viruses-AIDS Bacteria- gonorrhea Fungi- Athlete’s Foot Protozoa- African Sleeping Sickness Flatworms- Tapeworm Roundworms- Nematode
12.1.3 Through fluids such as semen, saliva, and blood, disease causing agents are transmitted. Sometimes it is possible to contract them from the air, food, or insects.
12.1.4 The agent of gonorrhea is Neisseria gonorrhoeae, a diplococcoid organism. Signs of its presence are readily apparent in men (pus discharge from the penis and painful urination) but are not readily apparent in women. Because of the latter fact, gonorrhea in women can quickly bloom into pelvic inflammatory disease, a serious problem that can lead to sterility. The gonorrhea organism can be passed along to infants during the birth process and if undetected can cause blindness and other problems.
12.1.5 AIDS is a condition in which the immune system is suppressed. The agent is HIV, a retrovirus that destroys helper T-calls and others. HIV preferentially attacks macrophages and helper T-calles, although other cells may also be targets. It is spread chiefly through contaminated body fluids. Any surface cut or abrasion is sufficient for transmission of the virus. HIV often follows a 10-year course, duing which there is gradual decline in helper T-cells and rise in HIV particles, ending in the rise of opportunistic infections commence. There is presently no effective treatment for AIDS. AZT can slow its progress by blocking reverse transcription, but its effect is temporary and it often produces serious side effects. With such an infectious disease in society, it is important to promote clean needles for drug users (when shooting heroin) and protected sex.
12.2 Types of Defense
12.2.1 Blood clotting is essential to any organism that relies on circulating fluids. It is an extremely complex and only partially understood process.
i. A vessel is damaged
ii. Platelets attach to the wound site, form lengthy extensions and adhere to collagen
fibers, forming what is essential a "plug."
iii. The platelets rupture, releasing a) vasoconstrictors that cause nearby vessels to constrict, thus reducing blood loss and b) thromboplastins (enzymes)
iv. In the presence of thromboplastins and calcium ions, prothrombin in the plasma becomes thrombinm a specific endopeptidase.
v. Thrombin breaks apart the large fibrinogen molecules of the plasma, the smaller piece of fibrous, a sticky protein called fiber.
vi. Fibrin fibers, along with damaged platelets, red blood cells, and white blood cells, form a net work that solidifies, becoming a clot that stops the bleeding.
vii. The clot contracts, pulling the wound together, further preventing bleeding and encouraging healing.
In hemophilia there is the absence of factor IX. Another reason for failure of the blood-clotting is an insufficency of calcium ions. An insufficency of vitamin K is an important cause of slow clotting. This vitamin is required by the liver for the synthesis of prothrombin.
12.2.2 Clonal selection is the process in which highly specific lines of virgin T-cells and B-cells are selected among millions of variants for activation and cell division. Those activated have cell surface receptors that match an antigen, either free or on the surface pathogen that has invaded the body. A key participant is the antigen-presenting cell. These cells, when bound to T-cells, secrete interleukin-1, a messanger that stimulates cell proliferation. Clones of T-cells arise, including memory cells.
12.2.3 Active Immunity- Immunity due to production of antibodies by the organism itself after the body’s defense mechanisms have been stimulate by invasion of foreign microrganisms.
12.2.4 Passive Immunity- Immunity due to acquisition of anti-bodies from another organism in which active immunity has been stimulated .
12.2.5 Natural Immunity- Immunity due to infection.
12.2.6 Artificial Immunity- Immunity due to inoculation with vaccine.
12.2.7 Lymphocytes form in primary lymphoid tissue (red bone marrow and thymus). T-cells differentiate in the thymus and B-cells in the red bone marrow. Mature lymphocytes reside in secondary lymphoid tissues (lymph nodes, tonsils, adenoids, spleen, small intestine). B-cells respond to infection with the humoral response, the formation and secretion of anti-bodies. T-cells carry out the cell-mediated response, the activation of T-cells. Both are prompted by antigens. Antibodies work through neutralizing antigens, activating complement, binding to viruses, clumping bacteria together and opsonization. Lymphosytes form highly specific cell surface receptor sites that include class I and class II MHC proteins, which are essential in identifying invaders, normal and infected body cells, and each other. Cytotoxic T-cells use their dual recognition sites to identify, attack and kill infected cells bearing the antigen tha brought about their arousal.
12.2.8 Monoclonal bodies- clones of selected B-cells, those producing the desired antibodies, or monoclonal antibodies, are produced through cell culturing techniques. To produce large clones, subject B-cells are fused with myeloma cells to form hybridomas. These are seperated and screened, and the desired cells are cultured and the antibodies are collected.
12.2.9 Explain the need for immunization against the bacterial infections: diphtheria, whooping cough and tetanus, and against viral infections: measles, polio and rubella.
12.2.10 Outline the process of Immunization
12.2.11 Discuss the benefits and danger of immunization against bacterial and viral infections
