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The Lymphatic System The Lymphatic System & Immunity& Immunity

The Lymphatic System The Lymphatic System & Immunity& Immunity

Chapter 17

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ImmunityImmunityImmunityImmunity

• 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

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Lymphatic SystemLymphatic SystemLymphatic SystemLymphatic 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

Figure 17.1Figure 17.1

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Lymphatic VesselsLymphatic VesselsLymphatic VesselsLymphatic Vessels

• Begin at lymphatic capillariesSlightly larger than blood capillariesOverlapping cells like one-way valvePressure will force fluid in

• Merge to form larger & larger vesselsThin walled and more valves than veins

• Periodically have lymph nodesLymphocytes in capsuled structure

thoracic duct L subclavian veinat junction with jugular

R. lymphatic duct R. subclavian vein

Figure 17.2aFigure 17.2a

Figure 17.2bFigure 17.2b

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Lymphatic flowLymphatic flowLymphatic flowLymphatic flow

• From tissue to veins• Pumped by muscle & respiratory

pumps like venous return

Figure 17.3Figure 17.3

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Lymphatic OrgansLymphatic OrgansLymphatic OrgansLymphatic Organs

• Primary lymphatic organs- stem cells divide & develop into mature B & T-cellsRed bone marrow & thymus

• Secondary organs: immune responses occurLymph nodes, spleen & lymphatic

nodules

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ThymusThymusThymusThymus

• 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 nodesLymph nodesLymph nodesLymph nodes

• Scattered throughout the bodyConcentrated near mammary glands,

axilla & groin

• Contain mature B-cells, T-cells dendritic cells and macrophages

• Filter lymph, trap foreign substancesMacrophages & lymphocytes destroy

most foreign substances

Figure 17.4Figure 17.4

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SpleenSpleenSpleenSpleen

• 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- Innate Immunity- BarriersBarriers

Innate Immunity- Innate Immunity- BarriersBarriers

• Skin: Physical & chemicalEpidermal structure & constant shedding

• Mucous membranes:Sticky mucus layer straps microbes, etc.

and cilia move it out • Fluids: tears, saliva, perspiration,

nasal secretionssDilute and antibacterial action

• Movement: flow of urine, defecation & vomiting

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Internal Defenses- Internal Defenses- ProteinsProteins

Internal Defenses- Internal Defenses- ProteinsProteins

• Interferons- interfere with viral reproduction in a cell

• Complement SystemEnhance other immune actionsBreak cell membranesAttract phagocytes Tag microbial cells for destruction

• Transferrins- bind iron & starve bacteria• Antimicrobial peptides: lyse microbes

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Internal Defenses-CellsInternal Defenses-CellsInternal Defenses-CellsInternal Defenses-Cells

• Phagocytes specialized to ingest microbes and cellular debrisNeutrophils Monocytes macrophages

• 5-10% of lymphocytes = Natural Killer (NK) CellsDestroy microbes & tumor cellsPresent in lymph nodes & red bone

marrow

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InflammationInflammationInflammationInflammation

• Response to tissue damageIndicated by redness, pain, heat &

swelling

1. damage mast cells, basophils & platelets release histamine

increased permeability & vasodilation in blood vessels

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Inflammation (Cont.)Inflammation (Cont.)Inflammation (Cont.)Inflammation (Cont.)

2. leakage of clotting proteins into tissue-Isolate bacteria behind clot

3. phagocytes attracted to siteNeutrophils & macrophages eat & die

4. pocket of dead cells = pusMoves to body surface or into cavity

& is cleared

Figure 17.5Figure 17.5

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FeverFeverFeverFever

• Abnormally high body temperatureNew set-point of thermoregulation

systemNormal temperature control action

with new set point.

• Stimulated by many toxins or internal signals : interleukin-1

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Adaptive ImmunityAdaptive ImmunityAdaptive ImmunityAdaptive Immunity

• Specifically directed against a particular type of invader

• Involves cell or antibody directed against a particular antigenAntigen can be any substance:

microbe, food, pollen, tissue

• Normally self–tolerant (does not attack normal body tissue)

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Maturation of T & B cellsMaturation of T & B cellsMaturation of T & B cellsMaturation of T & 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 ResponsesTypes of ResponsesTypes of ResponsesTypes of Responses

• Cell-mediated- T-cells attack directlyKiller 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 & AntibodiesAntigens & AntibodiesAntigens & AntibodiesAntigens & Antibodies

• Major Histocompatability Complex (MHC) = self antigens on cells surfaceUnique to each individual

• Allows T-cells to recognize foreign material• Antigen triggers plasma cell to produce

antibodiesY-shaped protein with variable antigen binding

site on armsOther end triggers recognition by phagocyte

Figure 17.6aFigure 17.6a

Figure 17.6bFigure 17.6b

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Triggering Adaptive Triggering Adaptive ResponseResponse

Triggering Adaptive Triggering Adaptive ResponseResponse

• 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 Processing & Presenting AntigensAntigens

Processing & Presenting Processing & Presenting AntigensAntigens

• 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

Figure 17.7Figure 17.7

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Cell Mediated ImmunityCell Mediated ImmunityCell Mediated ImmunityCell Mediated Immunity

• T-ceils also need costimulatorInterleukin-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

• Cytotoxic T cells – kill cellsWork against tumor cells transplanted cells &

infected cells• Memory T cells- hang around for years,

give rapid response

Figure 17.8Figure 17.8

Figure 17.9Figure 17.9

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B-cells and Antibody- B-cells and Antibody- Mediated ResponseMediated Response

B-cells and Antibody- B-cells and Antibody- Mediated ResponseMediated 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

Figure 17.11Figure 17.11

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Antibody Class ActionsAntibody Class ActionsAntibody Class ActionsAntibody Class Actions

• Neutralizing antigen-Binds & neutralizes toxins

• Immobilizing bacteria• Agglutinating-

Connect pathogens to one another easier phagocytosis

• Activating complement• Enhancing phagocytosis

Binding attracts phagocytes

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Immunological MemoryImmunological MemoryImmunological MemoryImmunological 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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AgingAgingAgingAging

• Thymus atrophies• Fewer responsive T cells• Thus poorer B cell response• Poorer response to new

infection