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Transcript
Chapter 17 Unit 1 The Lymphatic System & 17 Immunity Immunity 17 • Innate Immunity• fast, non-specific and no memory • Adaptive Immunity • Slower, specific & has a memory Lymphocytes: T-cells & B-cells Unit 1 Barriers, pH extremes, Phagocytes & NK cells, fever, inflammation, complement, interferon Lymphatic System 17 • Lymphatic tissue – • Bone marrow • Lymph- interstitial fluid in lymphatic vessels • Returns excess filtration from capillaries- to circulation • Transport dietary lipids • Maintenance & distribution- lymphoid organs • Filter bacteria and help active defenses Unit 1 reticular connective tissue containing lymphocytes Figure 17.1 Lymphatic Vessels 17 • Begin at lymphatic capillaries Slightly larger than blood capillaries Overlapping cells like one-way valve Pressure will force fluid in • Merge to form larger & larger vessels Thin walled and more valves than veins Lymphocytes in capsuled structure • thoracic duct L subclavian vein at junction with jugular • R. lymphatic duct R. subclavian vein Unit 1 • Periodically have lymph nodes Figure 17.2a Figure 17.2b Lymphatic flow 17 Unit 1 • From tissue to veins • Pumped by muscle & respiratory pumps like venous return Figure 17.3 Lymphatic Organs 17 • Primary lymphatic organs- stem cells divide & develop into mature B & Tcells • Secondary organs: immune responses occur Lymph nodes, spleen & lymphatic nodules Unit 1 Red bone marrow & thymus Thymus 17 Self reactive cells are removed Unit 1 • Two lobed organ • Posterior to sternum, medial to lungs & superior to heart • T-cells divide & mature Lymph nodes 17 • Scattered throughout the body • Contain mature B-cells, T-cells dendritic cells and macrophages • Filter lymph, trap foreign substances Macrophages & lymphocytes destroy most foreign substances Unit 1 Concentrated near mammary glands, axilla & groin Figure 17.4 • Between stomach & diaphragm • Contains blood filled venous sinuses and RBCs, macrophages, lymphocytes plasma cells & granular leukocytes • destroys worn or defective blood cells & platelets • Stores platelets • attacks foreign substances in blood • Fetal Hemopoiesis 17 Unit 1 Spleen Innate Immunity- Barriers 17 • Skin: Physical & chemical Epidermal structure & constant shedding • Mucous membranes: • Fluids: tears, saliva, perspiration, nasal secretionss Dilute and antibacterial action • Movement: flow of urine, defecation & vomiting Unit 1 Sticky mucus layer straps microbes, etc. and cilia move it out Internal Defenses- Proteins 17 • Interferonsinterfere with viral reproduction in a cell Enhance other immune actions Break cell membranes Attract phagocytes Tag microbial cells for destruction • Transferrins- bind iron & starve bacteria • Antimicrobial peptides: lyse microbes Unit 1 • Complement System Internal Defenses-Cells 17 • Phagocytes specialized to ingest microbes and cellular debris • 5-10% of lymphocytes = Natural Killer (NK) Cells Destroy microbes & tumor cells Present in lymph nodes & red bone marrow Unit 1 Neutrophils Monocytes macrophages Inflammation 17 • Response to tissue damage 1. damage mast cells, basophils & platelets release histamine increased permeability & vasodilation in blood vessels Unit 1 Indicated by redness, pain, heat & swelling Inflammation (Cont.) 17 2. leakage of clotting proteins into tissueIsolate bacteria behind clot 3. phagocytes attracted to site 4. pocket of dead cells = pus Moves to body surface or into cavity & is cleared Unit 1 Neutrophils & macrophages eat & die Figure 17.5 Fever 17 • Abnormally high body temperature • Stimulated by many toxins or internal signals : interleukin-1 Unit 1 New set-point of thermoregulation system Normal temperature control action with new set point. Adaptive Immunity 17 Antigen can be any substance: microbe, food, pollen, tissue • Normally self–tolerant (does not attack normal body tissue) Unit 1 • Specifically directed against a particular type of invader • Involves cell or antibody directed against a particular antigen • From stem cells in red bone marrow • B cells mature in bone marrow • T cells migrate to thymus • During maturation both make particular proteins in plasma membranes = antigen receptors 17 Unit 1 Maturation of T & B cells Types of Responses 17 • Cell-mediated- T-cells attack directly Killer T-cells produce specific antibodies • Helper T cells aid both cell- and antibody-mediated responses Unit 1 • Antibody-mediated• B cells become plasma cells Antigens & Antibodies 17 • Major Histocompatability Complex (MHC) = self antigens on cells surface Unique to each individual Y-shaped protein with variable antigen binding site on arms Other end triggers recognition by phagocyte Unit 1 • Allows T-cells to recognize foreign material • Antigen triggers plasma cell to produce antibodies Figure 17.6a Figure 17.6b Triggering Adaptive Response • • • • • Unit 1 requires recognizing the foreign antigen B-ceils can find it anywhere T-cells need presentation with MHC Antigen presenting cells (APC) do this APCs macrophages, dendritic cells & B cells • In respiratory, GI, urinary, reproductive tracts & lymph nodes 17 Processing & Presenting Antigens 17 • APC’s ingest & digest into fragments in vesicles • Synthesize MHC & pack in vesicles • Two vesicles fuse • Antigen-MHC complex inserted into plasma membrane • Presented to T-cells until a receptor matches & binds Unit 1 antigen fragments bind to MHC Figure 17.7 Cell Mediated Immunity 17 • T-ceils also need costimulator Interleukin-2 (IL-2) • Binding both response • T-cell begins rapidly dividing Forms a clone of many recognizing cells • Helper T cells- • Cytotoxic T cells – kill cells Work against tumor cells transplanted cells & infected cells • Memory T cells- hang around for years, give rapid response Unit 1 release IL2, attract phagocytes, stimulate macrophages & B cells Figure 17.8 Figure 17.9 • Hang out in lymph nodes • Respond to antigen (faster if presented) • With IL-2 enlarge, divide and become a clone of plasma cells • Plasma cells produce & release antibodies that bind the antigen • Some remain as Memory B Cells Ready to respond quickly if antigen met again 17 Unit 1 B-cells and Antibody- Mediated Response Figure 17.11 Antibody Class Actions 17 • Neutralizing antigenBinds & neutralizes toxins Connect pathogens to one another easier phagocytosis • Activating complement • Enhancing phagocytosis Binding attracts phagocytes Unit 1 • Immobilizing bacteria • Agglutinating- • Long lasting antibodies & lymphocytes • Many sensitive memory cells • Much larger & quicker response next time = Secondary Response • Primary response can be naturally acquired • or artificially acquired by vaccination Killed cells, isolated antigens, parts of viruses 17 Unit 1 Immunological Memory Aging 17 Unit 1 • Thymus atrophies • Fewer responsive T cells • Thus poorer B cell response • Poorer response to new infection