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Unit 8 Seminar Immunology The human immune system Made up of 2 branches that work together: 1. Innate (nonspecific) immune system First and second line of defense 2. Acquired (specific) immune system B and T cells The two branches work together to fight infectious agents Chemically controlled innate (nonspecific) immunity First and second line of defense Innate immunity- first line of defense • Intact skin • Mucous membranes • Normal microbiota Innate immunity- second line of defense • (phagocytic) white blood cells • Inflammation • Fever • Complement White Blood Cells (leukocytes) • • • • • Neutrophils: Phagocytic Basophils: Produce histamine Eosinophils: Toxic to parasites, some phagocytosis Dendritic cells: Initiate adaptive immune response, phagocytic Monocytes: Phagocytic as mature macrophages – Fixed macrophages in lungs, liver, bronchi – Wandering macrophages roam tissues • Lymphocytes: Involved in specific immunity. B and T cells. Phagocytosis of E.coli pseudopods of macrophage entrap E.coli bacteria bacteria brought into macrophage for destruction inflammation fever • Increases metabolic processes in the human body • Enhances inflammation, helps move WBCs • Some infectious agents induce fever The Complement System • Serum proteins activated in a cascade • Activated via one of three pathways • Activated Complement proteins trigger 3 primary immune responses 2. 1. 3. Figure 16.10 • The complement system is an important part of the innate immune system that has farreaching effects on the body’s ability to fight off infection. Many pathogens have the ability to affect or disable individual proteins within the Complement system. In your opinion, which Complement protein (C5a? C1?) would be most devastating to the host immune system if it were to be inactivated by a particular pathogen? Why? Acquired (specific) immunity B cells and T cells B cell immunity (humoral immunity) • Bone marrow gives rise to B cells • Some B cells (plasma cells) produce antibodies • Other B cells become long-lived memory cells T Cell immunity (cellular immunity) • T cells primarily respond to intracellular Ags • Differentiate in the thymus, then migrate to lymphoid tissue • Helper T Cells (CD4, TH) – TH1 – TH2 Activate cytotoxic T cells Activate B cells to produce antibodies • Cytotoxic T Cells (CD8, TC) – Destroy target cells with perforin Other immune components • Cytokines • Chemokines • Other chemical messengers • As you have learned in this unit, the immune system does an exceptional job in clearing infections from the host. However, on occasion the immune system can actually make an illness worse by overreacting to a potential pathogen. One example is a phenomenon called “cytokine storm”. This occurrence takes place when the body is infected by specific pathogens. Some examples include the influenza virus that caused the 1918 Spanish Flu epidemic and more recently the SARS epidemic in 2003. What occurs during “cytokine storm” and how does it Cytokine storm & Avian Flu • “Acute respiratory viral infection (especially from the H5N1 subtype influenza virus) results in a cytokine storm effecting the lungs, and subsequent damage to alveoli and lung tissue results in the lethality seen in more severe flu viral infections, especially those fatalities among young healthy adults” http://www.cytokinestorm.com/ accessed July 21, 2011 • Human society has evolved significantly over the past few decades. Populations of humans used to inhabit wide-open spaces and rarely had contact with large crowds of people. However, modern society requires people to live in very tight quarters and come into contact with possibly hundreds or thousands of people in a single day. Consider cities like New York City and Tokyo, Japan. Occupants in these cities are packed in tightly into subway systems and overcrowded conditions. When people in Japan are ill, they wear face masks to protect others, while in New York City this is not done. What are some other ways that people in these cities Unit 8 Assignment Unit 8 assignment: Microbial evasion of host immune defenses Microbiology encompasses many aspects of pathogens and human reactions to infections. This project will allow you to trace pathogens through the infection cycle and human response to the infection. Project requirements: Refer to Table 1.1 and answer the following questions for EACH organism listed above. Word requirements are outlined for each question - this represents a minimum number of words required. For each question answer in full and complete sentences, and provide both examples and scientific evidence to support your answer. Be sure to include a well-developed introduction and conclusion in your paper. You may use outside sources, but the reading material for Units 7 and 8 should provide the majority of information you will need to complete the assignment. Be sure to include all references in APA format. Table 1.1 Organism Strategy to avoid host immune system Common disease Trypanosoma cruzi Changes surface antigens to avoid immune system detection American trypanosomiasis Human immunodeficiency virus (HIV) Virus infects and hides in macrophages and CD4 Tcells. Acquired immunodeficiency syndrome (AIDS) Streptococcus pneumoniae Produce M proteins to inhibit phagocytes from attaching Pneumonia Questions: 1. Give a brief overview of the disease including signs and symptoms. Who is typically affected by this infection?(Children? Immunocompromised patients?)? What is the pathogens’ portal of entry and exit? (100 word minimum) 2. How would the innate immune system react to this pathogen? Which components would react? (75 word minimum) 3. Would this pathogen primarily stimulate cell-mediated immunity or antibodymediated immunity (T cells or B cells?) Why? (75 word minimum) 4. All of the organisms listed above have the ability to evade the host immune system, at least temporarily. Review Table 1.1 for the pathogens’ strategies used to avoid the host’s immune system. Why is this particular strategy helpful to the pathogen? How would this impact the pathogens’ ability to cause infection? How would the immune system compensate? (200 word minimum) To access an archived seminar consult the Flex Seminar guide in Doc Sharingstep by step instructions provided Questions?? References • Tortora, G., Funke, B., & Case, C. (2007). Microbiology: An Introduction (8th ed.). San Francisco, CA: Pearson.