Jeanne A PawitanHistology of the immune (lymphoid, lymphatic) systemJeanne Adiwinata PawitanDept. of HistologyFMUI

Jeanne A Pawitan

Jeanne A PawitanImmune systemCells of the immune systemBone marrow (myeloid tissue)Diffuse lymphoid systemDiffuse lymphoid tissueLymph (lymphoid) nodulesLymphoid organs - capsule

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Jeanne A PawitanImmune system defense mechanismFunction: protection >< foreign elementsForeign macromoleculesInvasive microorganismsVirusesBacteriaOthers Transformed cells

Jeanne A Pawitan

Jeanne A PawitanDefence mechanism (Martini)Non specific defensesPhysical barriersPhagocytes (M, neutro, eosinophils, monocytes)Immunological surveillance: NK cellsInterferons, complement systemInflammatory responses, feverSpecific defenses specific immunity specific immune responseInnate (human >< animal disease, except AIDS)Acquired

Jeanne A Pawitan

Jeanne A PawitanImmune responseSpecific recognition system (specific immune system)Recognize self >< non selfComponent Cellular (lymphocytes B, T)Soluble (Ig)Nonspecific (innate) effector system (non specific immune system)Amplifies function specific system

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Jeanne A PawitanNonspecific immune systemSoluble componentComplement proteins (cytokines): lymphokines-monokines: interleukines (ILs), interferons (IFNs), tumor necrosis factors (TNFs), transforming growth factors (TGFs), hematopoietic colony-stimulating factors (CSFs)Cellular component phagocytes:Blood: neutrophils, eosinophils, monocytesTissue: macrophages (alveolar macrophages, Kupffers cells, synovial cells joint cavities, perivascular microglial cells CNS)

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Jeanne A PawitanBone marrow (red) myeloid tissueLocation: central (marrow, medullary) cavity long bonesInterstices (trabeculae) spongy/cancelous bonesSoft, gelatinous, highly vascular cellular tissueFunction: hemopoiesis 5th month prenatalLM: vascular compartment (A., V., sinusoids)Intervening spaces hemopoietic compartments meshwork - islands of hemopoietic cells Adventitial reticular cells, reticular fibers

Jeanne A Pawitan

Jeanne A PawitanBone marrow cellsHemopoietic cellsBlood cells various stagesMacrophages destroyedNuclei erythrocytes precursorsMalformed cellsExcess cytoplasmAdventitial reticular cells By age 20 adult: cytoplasm - accumulate fat adipose cells large reduce hemopoietic compartment yellow marrow

Jeanne A Pawitan

Jeanne A PawitanDiffuse lymphoid systemNon-encapsulatedLocation: Lymphoid organsMucosa (lamina propria) mucosa associated lymphoid tissue (MALT)Digestive system (Gut ALT): Peyers patchesRespiratory system (Bronchus ALT)Urinary systemOccur asDiffuse lymphoid tissue = localized lymphocyte infiltrationLymphoid nodules (lymphonodulus)

Jeanne A Pawitan

Jeanne A PawitanDiffuse lymphoid tissueConsists ofStroma Reticular fibers silver impregnationReticular cells of mesenchymal origin some are phagocytic fixed macrophagesLymphocytes Free macrophagesPlasma cells

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Jeanne A PawitanReticular cellsShape: elongate stellateNucleus: ovoid euchromaticCytoplasm:ScantyAcidophilic ContainsRER fewGolgi complex moderate-well developedFine filaments bundles at periphery

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Jeanne A PawitanLymph (lymphoid, lymphatic) nodule, lymphonodulus lymphoid follicles=circumscribed-spherical/ovoid-closely packed-lymphocytesIn diffuse lymphoid tissueLocation:Lymph node cortexSpleen white pulpTonsils Lamina propria (MALT): Peyers patches, etc.

Jeanne A Pawitan

Jeanne A PawitanGut-associated lymphoid tissueIsolated lymphoid folliclesPeyers patches aggregates ileumLymphoid folliclesB cellsT cells looser surrounding B CellsNumerous APC surrounding B cellsSimple columnar epithelium M (microfold) cells capture Ag present their epitopes to lymphocytesAfferent lymph vessels (-), Efferent lymph drainage (+)Received small arterioles capillary bed high endothelial lined venules (HEVs)Lymphocytes entering Peyers patches have homing receptors specific for HEVs of GALT

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Jeanne A PawitanBronchus-associated lymphoid tissue Peyers patches walls bronchus esp. bronchi-bronchiole bifurcateEpithelial cover: pseudostratified ciliated columnar epithelium with goblet cells M cellsAfferent lymph vessels (-)Efferent lymph drainage (+)Rich vascular supply HEVsPossible systemic and localized role in immune responseLymphocytes entering BALT have homing receptors for HEVs of BALTCells: mostly B cells, also APC, T cells

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Jeanne A PawitanLymphoid organsThymus (primary lymphoid organ)Lymph nodes (lymphonodus)Spleen (lien)Tonsils (tonsila)

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Jeanne A PawitanThymus Location: superior mediatinum anterior of great vessels (aorta)After puberty involution (atrophy) adult adipose cells 2 lobes Encapsulated dense-irregular-collagenous connective tissue septa (trabecula) lobes incomplete lobules

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Jeanne A PawitanLymph nodeLocation: interposed in the path of lymph vessels-esp.Neck, axila, groinAlong major vessel body cavitiesFunctions:Filter removeBacteriaForeign substances

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Jeanne A PawitanLymph nodeSmall, soft, < 3 cmCapsule fibrous connective tissue (thickened at hilum) - trabeculae - adipose tissue Convex: afferent lymph vessels valvesConcave = hilum: A., V., efferent lymph vessels valves medulla

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Jeanne A PawitanLymph node - sinuses Sinuses: network stellate reticular cells macrophages endothelial-like simple squamous epithelium migratory lymphoid cellsCourse:Afferent lymphatic vesselsSubcapsular sinusCortical (paratrabecular) sinusesMedullary sinusesEfferent lymphatic vessels

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Jeanne A PawitanLymph nodeHistologically:Cortex antigen-presenting follicular dendritic cellsPrimary lymphoid nodules (virgin B & memory B cells)Secondary nodules (with germinal centers) antigenic challenge B memory & plasma cellParacortex Thymus dependent zoneMedulla

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Jeanne A PawitanLymph node - medullaTrabeculae from hilumMedullary cordsNetwork reticular fiber reticular cellsCells Lymphocytes migrating from cortex medullary sinusesPlasma cellsMacrophages

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Jeanne A PawitanLymph node - vascularizationArtery (hilum) trabeculae medulla medullary cords Capillary beds in medullaCortex cortical capillary beds postcapillary venules (paracortex) vein - hilum

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Jeanne A PawitanSpleen (lien)Largest lymphoid organUpper left quadrant abdominal cavity Intraperitoneal visceral peritoneumFunction:Proliferation B, T cellsAb formation blood-borne Ag inactivationElimination of Ag, bacteria, particles, etc.Filtering blood destroying old erythrocytesHemopoietic (fetal) adult when needed

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Jeanne A PawitanSpleen (lien)Convex surfaceConcave surface hilum capsule-thickenedArteries nerve fibers (in)Veins lymph vessels (out)Dense irregular connective tissue capsule - occasional smooth muscle cells trabeculae into the organ

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Jeanne A PawitanSpleen (lien)Histology Network reticular fibers reticular cells attached to capsule trabeculae blood vesselsFresh - cut - parenchymaGrey area = white pulp (Marginal zone 100 m wide between white red pulp)Surrounding red area = red pulp (splenic cords of Billroth)

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Jeanne A PawitanSpleen (lien) blood supplySplenic artery - hilum branching trabecular arteries ( 0.2mm) central arteries periarterial lymphatic sheath (PALS) Radiating - slender blood vessels red pulp (recur) -marginal sinuses marginal zonebranching penicillar arteries red pulp: Pulp arterioleSheated arteriole Schweigger-Seidel sheath macrophages)Terminal arterial capillaries splenic sinuses Veins of the pulp splenic vein portal vein

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Jeanne A PawitanClosed circulation open circ.Closed circulationEndothelial lining: terminal arterial capillaries continuous - sinusesOpen circulationTerminal arterial capillaries red pulp - sinusesCombination of both

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Jeanne A PawitanSpleen (lien) white pulpCentral arteriolePALS: T lymphocytesFrequently: lymphoid nodules (B cells) germinal center = antigenic challenge central arteriole - periphery

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Jeanne A PawitanSpleen (lien) red pulp spongeSpaces = splenic (venous) sinuses (sinusoids)Endothelial lining fusiform staves of a barrelBetween endothelial cells - spaces - 2-3 m Surrounded by reticular fibers (continuous with splenic cords) thin strands longitudinal axisHave a discontinuous basal laminaSponge material = splenic cords of BillrothReticular fibers (collagen III) loose network interstices permeated by extravasated bloodStellate reticular cells isolate coll III from blood >< platelet reaction to coll >< coagulationMacrophages particularly numerous near sinusoids

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Jeanne A PawitanSpleen histophysiologyMacrophages Marginal sinuses macrophage richPeriphery of splenic sinusesPhagocytosisAg, bacteria, particulate matter, etcOld erythrocytesLess fkexible (old, malaria) cannot penetrate spaces between endotheliumSurface coat: sialic acid residue (-) galactose moieties exposed induced phagocytosis

Jeanne A Pawitan

Jeanne A PawitanSpleen histophysiologyLymphocytes -Ag challenge white pulp B memory cells, plasma cells lymphoid nodulesT cells (various subcategories) PALS marginal sinuses Site of Ag challenge Circulating pool of lymphocytesPlasma cellsSome stay in marginal zone Ab marginal sinusesMost bone marrow Ab bone marrow sinuses

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Jeanne A PawitanTonsils: palatine, pharyngeal, lingualIncompletely encapsulatedAggregates of lymphoid nodulesGuard the entrance of oral (oro) pharynxExposed to Airborne AgIngested AgReaction to AgForming lymphocytesMounting immune response

Jeanne A Pawitan