Transcript 17 Unit 1 - Cloudfront.net

Chapter 17
Unit 1
The Lymphatic System &
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Immunity
Immunity
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• Innate Immunity• fast, non-specific and no memory
• Adaptive Immunity
• Slower, specific & has a memory
Lymphocytes: T-cells & B-cells
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Barriers, pH extremes, Phagocytes & NK
cells, fever, inflammation, complement,
interferon
Lymphatic System
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• 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
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reticular connective tissue containing lymphocytes
Figure 17.1
Lymphatic Vessels
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• 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
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• Periodically have lymph nodes
Figure 17.2a
Figure 17.2b
Lymphatic flow
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• From tissue to veins
• Pumped by muscle & respiratory
pumps like venous return
Figure 17.3
Lymphatic Organs
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• Primary lymphatic organs- stem cells
divide & develop into mature B & Tcells
• Secondary organs: immune
responses occur
Lymph nodes, spleen & lymphatic
nodules
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Red bone marrow & thymus
Thymus
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Self reactive cells are removed
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• Two lobed organ
• Posterior to sternum, medial to lungs
& superior to heart
• T-cells divide & mature
Lymph nodes
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• 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
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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
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Spleen
Innate Immunity- Barriers
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• 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
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Sticky mucus layer straps microbes, etc. and
cilia move it out
Internal Defenses- Proteins
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• 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
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• Complement System
Internal Defenses-Cells
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• 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
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Neutrophils
Monocytes macrophages
Inflammation
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• Response to tissue damage
1. damage mast cells, basophils &
platelets release histamine
 increased permeability &
vasodilation in blood vessels
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Indicated by redness, pain, heat &
swelling
Inflammation (Cont.)
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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
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Neutrophils & macrophages eat & die
Figure 17.5
Fever
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• Abnormally high body temperature
• Stimulated by many toxins or
internal signals : interleukin-1
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New set-point of thermoregulation
system
Normal temperature control action with
new set point.
Adaptive Immunity
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Antigen can be any substance: microbe,
food, pollen, tissue
• Normally self–tolerant
(does not attack normal body tissue)
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• 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
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Maturation of T & B cells
Types of Responses
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• Cell-mediated- T-cells attack directly
Killer T-cells
produce specific antibodies
• Helper T cells aid both cell- and
antibody-mediated responses
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• Antibody-mediated• B cells become plasma cells
Antigens & Antibodies
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• 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
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• Allows T-cells to recognize foreign material
• Antigen triggers plasma cell to produce
antibodies
Figure 17.6a
Figure 17.6b
Triggering Adaptive Response
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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
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• 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
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antigen fragments bind to MHC
Figure 17.7
Cell Mediated Immunity
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• 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
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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
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B-cells and Antibody- Mediated
Response
Figure 17.11
Antibody Class Actions
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• Neutralizing antigenBinds & neutralizes toxins
Connect pathogens to one another easier
phagocytosis
• Activating complement
• Enhancing phagocytosis
Binding attracts phagocytes
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• 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
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Immunological Memory
Aging
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• Thymus atrophies
• Fewer responsive T cells
• Thus poorer B cell response
• Poorer response to new infection