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Chapter 3

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Biomedical Physio & Kines
BPK 140
Michael Walsh

1 KIN 140 Section 3 Dr Mike Walsh I. Immunity Any microorganism, foreign protein, or abnormal cell that activates the immune system is called an antigen (antibody generator). When a disease-causing agent attacks the body, it encounters 3 major lines of defense. First line of defense is non-specific and is part of the innate immune system and consists of the following: 1) physical barriers (skin, mucous membranes, cilia) 2) chemical barriers (saliva, sweat,sebum, tears, lysozyme, digestive enzymes, lactoferrin, urine) 3) resident bioflora (beneficial microbes living on our skin and in our bodies that help block infection by disease-causing microbes). The second line of defense is also part of the non-specific, innate immune system and includes the following: 1) non-specific immune cells (eosinophils, basophils, neutrophils, macrophages) 2) chemical mediators (interleukin-1, interferon, complement) 3) fever 4) inflammation 5) phagocytosis The third line of defense is part of the adaptive or acquired immune system. This line of defense provides specific, long-term protection against microbes. The third line of defense includes the following: 1) T-cells (helper and cytotoxic) 2) B-cells (memory and plasma cells) 3) antibodies 2 A. Immunity Cells The cellular defense mechanisms consist of various white blood cells produced by bone marrow: Macrophages: very large white blood cells that devour pathogens and worn out cells Neutrophils: another white blood cell type that ingests pathogens Natural killer cells: destroy pathogens, cells infected with pathogens, and cancerous cells. Lymphocytes: Large: cells like natural killer cells are part of the innate system. They kill lots of pathogens or cells with pathogens inside and cancerous cells. Small: T cells (helper T cells, killer T cells, suppressor T cells, and memory T cells) and B cells (produce antibodies and retain memory). Both are part of our adaptive immune system. B cells (produce antibodies and retain memory) B. The Immune Response (Fig 13-1) Avirus (for example) enters the blood stream. The following 10 steps are a general overview of a successful defense. 1. Scavenger cells such as neutrophils recognize the virus as foreign and destroy some of the viruses. This response is rapid but short-lived. 2. Resident antibodies with enough specificity will attack the virus. 3. Macrophages also devour the invading viruses and signal helper T cells. (first 3 steps are identifying the antigen) 4. Macrophages, the clever scavengers that they are, take surface proteins of the virus a put them on their cell membrane. This macrophage antigen activates T helper cells. 5. Helper T cells multiply and activate B and killer T cells production in the spleen and lymph nodes. 6. B cells multiply and in our lymph nodes (this is why your lymph nodes swell) end up doing two things: 1. many transform into plasma cells that produce antibodies that work as a ‘lock and key’antibody production (2,000 per second per cell). 2. and some become memory B cells (see 10). 3 7. Antibodies bind to the virus and will destroy them or make them more vulnerable to destruction by macrophages. 8. Killer T cells destroy both viruses and the body’s own cells that have been infected with the virus. 9. T suppressor cells monitor antibody production and down-regulate it when the destruction of viruses is succeeding. 10. Some T and B cells become memory cells able to launch a quicker and more successful attack against future invasion of the same antigen. Furthermore, circulating antibodies are now present. Many of the asymptomatic symptoms produced early in the infection are due to the immune response. Lymp
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