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Unit 10 notes: The Immune System Name:_________________________________________ Pathogen: a disease causing agent Most pathogens are infectious microbes such as bacteria or viruses that are capable of causing disease (many produce toxins). Other parasitic organisms such as fungi and some protozoans are also considered pathogens. NOT ALL microbes are harmful, the word pathogen refers specifically only to microbes that cause disease. Non-Specific Immunity The body has a number of defenses in the immune system that fight off pathogens Some defenses are considered non-specific because they are not aimed at a specific pathogen o Help to prevent a disease o If disease does occur, this helps to slow the spread of the disease. 1. Skin Barrier Dead skin cells help protect against invasion by microorganisms. Some bacteria live on our skin symbiotically. They digest oils produced by the skin and then secrete a mild acid that inhibits many pathogens. 2. Chemical Barriers Saliva, tears, and mucus contain lysozyme. Lysozyme: an enzyme that breaks down bacterial cell walls killing the bacteria. Mucus acts as a protective barrier by blocking bacteria from sticking to the epithelial cells (cells under the mucus lining). Non-Specific Responses to invasion If a pathogen gets through the non-specific barriers there are 3 non-specific responses that may occur. 3. Cellular Defense Phagocytosis: Process in which a phagocytic cell surrounds and internalizes a foreign microorganism. Once the pathogen is internalized the phagocyte releases digestive enzymes and other chemicals from their lysozomes to destroy the pathogen. 4. Interferon Virus infected cells secrete a protein called interferon. Interferon binds to neighboring cells and causes those cells to produce antiviral proteins so those cells aren’t infected with the virus. Interferon allows cells to communicate to the immune system to eradicate a pathogen or a tumor. 5. Inflammatory Response Increased blood flow to the infected area makes blood vessels more permeable to allow white blood cells to enter the infected area. Unit 10 notes: The Immune System Name:_________________________________________ Specific Immunity Lymphatic system Organs and cells that filter lymph fluid and destroy pathogens. Lymphocytes: a type of white blood cell (WBC) produced in the bone marrow Lymph nodes, tonsils, spleen, thymus gland & other tissues in mucous membranes in the intestinal, respiratory, urinary, and genital tracts. Four Important Immune Cells B-Cells Helper T-Cells Killer T-Cells Memory Cells Antigen: A substance on a pathogen that causes the immune system to produce antibodies. Antigens have marker molecules (proteins) on their surface that have unique shapes making them identifiable to other cells. Antibody: A substance produced by the immune system in response to (against) an antigen B-Cell Response An activated helper T-Cell presents processed antigens (from a pathogen) to a B-Cell. B-Cell: manufactures antibodies to bind the antigen in the body. The antibodies enhance immune system response by binding to pathogens making them more susceptible to phagocytic destruction and also speed up inflammation and non-specific response. Located in all lymphatic tissues T-Cell Response Helper T-Cells: Bind to & activate cytotoxic T-Cells (Killer T Cells) to help fight a pathogen Activated Killer T-Cells: Destroy pathogens and release chemicals called cytokines. Cytokines help to stimulate the immune system. Especially good at killing virus infected cells Passive Immunity Passive Immunity: Temporary protection produced when antibodies made by other people or animals are transferred into the body. Active Immunity Active Immunity: Long term immunity that occurs after the immune system has been exposed to disease and memory cells have been produced. Unit 10 notes: The Immune System Name:_________________________________________ Secondary Response To Antigen This occurs when the immune system is re-exposed to a particular antigen. Faster response compared to the primary exposure B and T-Cell response is greater during a secondary exposure The memory of the antigen lasts longer (more memory cells produced) Memory Cells: Remember antigens of pathogens we have been exposed to in the past so our body can quickly destroy the pathogen if it enters the body again.