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Copyright 2010, John Wiley & Sons, Inc.
Chapter 17
The Lymphatic System and Immunity
Copyright 2010, John Wiley & Sons, Inc.
Immunity Innate Immunity Fast, non-specific and no memory
Barriers, pH extremes, Phagocytes & NK cells, fever, inflammation, complement, interferon
Adaptive Immunity Slower, specific & has a memory
Lymphocytes: T-cells & B-cells
Copyright 2010, John Wiley & Sons, Inc.
Lymphatic System Lymphatic tissue
Reticular connective tissue containing lymphocytes
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
Copyright 2010, John Wiley & Sons, Inc.
Lymphatic System
Copyright 2010, John Wiley & Sons, Inc.
Lymphatic Vessels 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
Periodically have lymph nodes Lymphocytes in capsuled structure
thoracic duct L subclavian vein At junction with jugular
R. lymphatic duct R. subclavian vein
Copyright 2010, John Wiley & Sons, Inc.
Lymphatic Vessels
Copyright 2010, John Wiley & Sons, Inc.
Lymphatic Vessels
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Lymphatic Flow From tissue to veins Pumped by muscle & respiratory pumps like
venous return
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Lymphatic Flow
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Lymphatic FlowInteractions Animation
Lymph Formation and Flow
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Copyright 2010, John Wiley & Sons, Inc.
Lymphatic Organs Primary lymphatic organs- stem cells divide &
develop into mature B & T-cells Red bone marrow & thymus
Secondary organs: immune responses occur Lymph nodes, spleen & lymphatic nodules
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Thymus Two lobed organ Posterior to sternum, medial to lungs &
superior to heart T-cells divide & mature
Self reactive cells are removed
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Lymph Nodes Scattered throughout the body
Concentrated near mammary glands, axilla & groin
Contain mature B-cells, T-cells dendritic cells and macrophages
Filter lymph, trap foreign substances Macrophages & lymphocytes destroy most foreign
substances
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Lymph Nodes
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Spleen 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
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Innate Immunity: Barriers Skin: physical and chemical
Epidermal structure & constant shedding Mucous membranes
Sticky mucus layer straps microbes, etc. and cilia move it out
Fluids: tears, saliva, perspiration, nasal secretions Dilute and antibacterial action
Movement: flow of urine, defecation & vomiting
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Internal Defenses: Proteins Interferons
Interfere with viral reproduction in a cell Complement System
Enhance other immune actions Break cell membranes Attract phagocytes Tag microbial cells for destruction
Transferrins- bind iron and starve bacteria Antimicrobial peptides: lyse microbes
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Internal Defenses: Cells Phagocytes specialized to ingest microbes
and cellular debris Neutrophils Monocytes macrophages
5-10% of lymphocytes = Natural Killer (NK) Cells Destroy microbes & tumor cells Present in lymph nodes & red bone marrow
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Inflammation Response to tissue damage
Indicated by redness, pain, heat & swelling
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Inflammation1. Damage mast cells, basophils & platelets
release histamine
increased permeability & vasodilation in blood vessels
2. Leakage of clotting proteins into tissue- Isolate bacteria behind clot
3. Phagocytes attracted to site Neutrophils & macrophages eat & die
4. Pocket of dead cells = pus Moves to body surface or into cavity & is cleared
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Inflammation
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Fever Abnormally high body temperature
New set-point of thermoregulation system Normal temperature control action with new set
point Stimulated by many toxins or internal signals
Interleukin-1
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Adaptive Immunity Specifically directed against a particular type
of invader Involves cell or antibody directed against a
particular antigen Antigen can be any substance: microbe, food,
pollen, tissue Normally self–tolerant
Does not attack normal body tissue
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Maturation of T and B cells 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
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Types of Responses Cell-mediated- T-cells attack directly
Killer T-cells Antibody-mediated B cells become plasma cells
Produce specific antibodies Helper T cells aid both cell- and antibody-
mediated responses
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Antigens & Antibodies Major Histocompatability Complex (MHC) = self
antigens on cells surface Unique to each individual
Allows T-cells to recognize foreign material Antigen triggers plasma cell to produce antibodies
Y-shaped protein with variable antigen binding site on arms
Other end triggers recognition by phagocyte
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Antigens & Antibodies
Copyright 2010, John Wiley & Sons, Inc.
Antigens & Antibodies
Copyright 2010, John Wiley & Sons, Inc.
Triggering Adaptive Response 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
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Processing & Presenting Antigens APC’s ingest & digest into fragments in
vesicles Synthesize MHC & pack in vesicles Two vesicles fuse
Antigen fragments bind to MHC Antigen-MHC complex inserted into plasma
membrane Presented to T-cells until a receptor matches
& binds
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Processing & Presenting Antigens
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Cell Mediated Immunity 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
Release IL2, attract phagocytes, stimulate macrophages & B cells
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Cell Mediated Immunity Cytotoxic T cells – kill cells
Work against tumor cells transplanted cells & infected cells
Memory T cells- hang around for years, give rapid response
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Cell Mediated Immunity
Copyright 2010, John Wiley & Sons, Inc.
Cell Mediated Immunity
Copyright 2010, John Wiley & Sons, Inc.
B-cells and Antibody-Mediated Response 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
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Secretion of Antibodies
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Antibody Class Actions Neutralizing antigen
Binds and neutralizes toxins Immobilizing bacteria Agglutinating
Connect pathogens to one another easier phagocytosis
Activating complement Enhancing phagocytosis
Binding attracts phagocytes
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Immunological Memory 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
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Immunological MemoryInteractions Animation
Introduction to Disease Resistance
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Aging Thymus atrophies Fewer responsive T cells Thus poorer B cell response Poorer response to new infection
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End of Chapter 17
Copyright 2010 John Wiley & Sons, Inc.All rights reserved. Reproduction or translation of this work beyond that permitted in section 117 of the 1976 United States Copyright Act without express permission of the copyright owner is unlawful. Request for further information should be addressed to the Permission Department, John Wiley & Sons, Inc. The purchaser may make back-up copies for his/her own use only and not for distribution or resale. The Publishers assumes no responsibility for errors, omissions, or damages caused by the use of theses programs or from the use of the information herein.
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