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Jeanne A Pawitan Histology of the immune (lymphoid, lymphatic) system Jeanne Adiwinata Pawitan Dept. of Histology FMUI.

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Presentation on theme: "Jeanne A Pawitan Histology of the immune (lymphoid, lymphatic) system Jeanne Adiwinata Pawitan Dept. of Histology FMUI."— Presentation transcript:

1 Jeanne A Pawitan Histology of the immune (lymphoid, lymphatic) system Jeanne Adiwinata Pawitan Dept. of Histology FMUI

2 Jeanne A Pawitan Immune system Cells of the immune system Bone marrow (myeloid tissue) Diffuse lymphoid system °Diffuse lymphoid tissue °Lymph (lymphoid) nodules Lymphoid organs - capsule

3 Jeanne A Pawitan Immune system – defense mechanism Function: protection >< foreign elements °Foreign macromolecules °Invasive microorganisms Viruses Bacteria Others °Transformed cells

4 Jeanne A Pawitan Defence mechanism (Martini) Non specific defenses °Physical barriers °Phagocytes (M, neutro, eosinophils, monocytes) °Immunological surveillance: NK cells °Interferons, complement system °Inflammatory responses, fever Specific defenses – specific immunity –specific immune response °Innate (human >< animal disease, except AIDS) °Acquired

5 Jeanne A Pawitan Immune response Specific recognition system (specific immune system) °Recognize self >< non self °Component Cellular (lymphocytes B, T) Soluble (Ig) Nonspecific (innate) effector system (non specific immune system) °Amplifies – function – specific system

6 Jeanne A Pawitan Nonspecific immune system Soluble component °Complement 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, monocytes °Tissue: macrophages (alveolar macrophages, Kupffer’s cells, synovial cells – joint cavities, perivascular microglial cells – CNS)

7 Jeanne A Pawitan Bone marrow (red) – myeloid tissue Location: °central (marrow, medullary) cavity – long bones °Interstices (trabeculae) – spongy/cancelous bones Soft, gelatinous, highly vascular – cellular tissue Function: hemopoiesis – 5 th month prenatal LM: °vascular compartment (A., V., sinusoids) °Intervening spaces hemopoietic compartments – meshwork - islands of hemopoietic cells Adventitial reticular cells, reticular fibers

8 Jeanne A Pawitan Bone marrow cells Hemopoietic cells °Blood cells – various stages °Macrophages – destroyed Nuclei – erythrocytes precursors Malformed cells Excess cytoplasm Adventitial reticular cells °By age 20 – adult: cytoplasm - accumulate fat ≈ adipose cells – large – reduce hemopoietic compartment  yellow marrow

9 Jeanne A Pawitan Diffuse lymphoid system Non-encapsulated Location: °Lymphoid organs °Mucosa (lamina propria) – mucosa associated lymphoid tissue (MALT) Digestive system (Gut ALT): Peyer’s patches Respiratory system (Bronchus ALT) Urinary system Occur as °Diffuse lymphoid tissue = localized lymphocyte infiltration °Lymphoid nodules (lymphonodulus)

10 Jeanne A Pawitan Diffuse lymphoid tissue Consists of °Stroma Reticular fibers – silver impregnation Reticular cells of mesenchymal origin – some are phagocytic ≈ fixed macrophages °Lymphocytes °Free macrophages °Plasma cells

11 Jeanne A Pawitan Reticular cells Shape: elongate – stellate Nucleus: ovoid – euchromatic Cytoplasm: °Scanty °Acidophilic °Contains RER – few Golgi complex – moderate-well developed Fine filaments – bundles – at periphery

12 Jeanne A Pawitan Lymph (lymphoid, lymphatic) nodule, lymphonodulus – lymphoid follicles =circumscribed-spherical/ovoid-closely packed-lymphocytes In diffuse lymphoid tissue Location: °Lymph node –cortex °Spleen – white pulp °Tonsils °Lamina propria (MALT): Peyer’s patches, etc.

13 Jeanne A Pawitan Gut-associated lymphoid tissue Isolated lymphoid follicles Peyer’s patches – aggregates – ileum °Lymphoid follicles B cells T cells – looser – surrounding B Cells Numerous APC – surrounding B cells °Simple columnar epithelium  M (microfold) cells – capture Ag  present their epitopes to lymphocytes °Afferent lymph vessels (-), °Efferent lymph drainage (+) °Received small arterioles  capillary bed  high endothelial lined venules (HEVs) °Lymphocytes entering Peyer’s patches have homing receptors – specific for HEVs of GALT

14 Jeanne A Pawitan Bronchus-associated lymphoid tissue ≈ Peyer’s patches – walls – bronchus – esp. bronchi-bronchiole bifurcate Epithelial cover: pseudostratified ciliated columnar epithelium with goblet cells  M cells Afferent lymph vessels (-) Efferent lymph drainage (+) Rich vascular supply  HEVs °Possible systemic and localized role in immune response °Lymphocytes entering BALT have homing receptors for HEVs of BALT Cells: mostly B cells, also APC, T cells

15 Jeanne A Pawitan Lymphoid organs Thymus (primary lymphoid organ) Lymph nodes (lymphonodus) Spleen (lien) Tonsils (tonsila)

16 Jeanne A Pawitan Thymus 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

17 Jeanne A Pawitan Lymph node Location: interposed in the path of lymph vessels-esp. °Neck, axila, groin °Along major vessel °body cavities Functions: °Filter – remove Bacteria Foreign substances

18 Jeanne A Pawitan Lymph node Small, soft, Ø < 3 cm Capsule – fibrous connective tissue (thickened at hilum) - trabeculae - adipose tissue Convex: afferent lymph vessels – valves Concave = hilum: A., V., efferent lymph vessels – valves  ← medulla

19 Jeanne A Pawitan Lymph node - sinuses Sinuses: network – stellate reticular cells – macrophages – endothelial-like simple squamous epithelium – migratory lymphoid cells Course: Afferent lymphatic vessels Subcapsular sinus Cortical (paratrabecular) sinuses Medullary sinuses Efferent lymphatic vessels

20 Jeanne A Pawitan Lymph node Histologically: °Cortex – antigen-presenting follicular dendritic cells Primary lymphoid nodules (virgin B & memory B cells) Secondary nodules (with germinal centers) – antigenic challenge  B memory & plasma cell °Paracortex – Thymus dependent zone °Medulla

21 Jeanne A Pawitan Lymph node - medulla Trabeculae – from hilum Medullary cords °Network – reticular fiber – reticular cells °Cells Lymphocytes – migrating from cortex  medullary sinuses Plasma cells Macrophages

22 Jeanne A Pawitan Lymph node - vascularization Artery (hilum)  trabeculae  medulla  medullary cords  °Capillary beds in medulla °Cortex – cortical capillary beds  postcapillary venules (paracortex)  vein - hilum

23 Jeanne A Pawitan Spleen (lien) Largest lymphoid organ Upper left quadrant – abdominal cavity Intraperitoneal – visceral peritoneum Function: °Proliferation B, T cells °Ab formation – blood-borne Ag inactivation °Elimination of Ag, bacteria, particles, etc. °Filtering blood – destroying old erythrocytes °Hemopoietic (fetal) – adult – when needed

24 Jeanne A Pawitan Spleen (lien) Convex surface Concave surface – hilum – capsule- thickened °Arteries – nerve fibers (in) °Veins – lymph vessels (out) Dense – irregular connective tissue – capsule - occasional smooth muscle cells – trabeculae  into the organ

25 Jeanne A Pawitan Spleen (lien) Histology °Network – reticular fibers – reticular cells – attached to capsule  trabeculae – blood vessels °Fresh - cut - parenchyma Grey area = white pulp (Marginal zone – 100 μm wide – between white – red pulp) Surrounding red area = red pulp (splenic cords of Billroth)

26 Jeanne A Pawitan Spleen (lien) – blood supply Splenic artery - hilum  branching  trabecular arteries (  0.2mm)  central arteries – periarterial lymphatic sheath (PALS)  °Radiating - slender blood vessels  red pulp  (recur) - marginal sinuses – marginal zone °branching  penicillar arteries – red pulp: Pulp arteriole Sheated arteriole – Schweigger-Seidel sheath – macrophages) Terminal arterial capillaries – splenic sinuses  Veins of the pulp  splenic vein  portal vein

27 Jeanne A Pawitan Closed circulation – open circ. Closed circulation °Endothelial lining: terminal arterial capillaries –continuous - sinuses Open circulation °Terminal arterial capillaries – red pulp - sinuses Combination of both

28 Jeanne A Pawitan Spleen (lien) – white pulp Central arteriole PALS: °T lymphocytes °Frequently: lymphoid nodules (B cells) – germinal center = antigenic challenge  central arteriole - periphery

29 Jeanne A Pawitan Spleen (lien) – red pulp  sponge °Spaces = splenic (venous) sinuses (sinusoids) Endothelial lining – fusiform  staves of a barrel Between endothelial cells - spaces  m Surrounded by reticular fibers (continuous with splenic cords) – thin strands ┴ longitudinal axis Have a discontinuous basal lamina °Sponge material = splenic cords of Billroth Reticular fibers (collagen III) – loose network – interstices permeated by extravasated blood Stellate reticular cells – isolate coll III from blood > < coagulation Macrophages particularly numerous near sinusoids

30 Jeanne A Pawitan Spleen –histophysiology Macrophages °Marginal sinuses – macrophage rich °Periphery of splenic sinuses  Phagocytosis  Ag, bacteria, particulate matter, etc  Old erythrocytes  Less fkexible (old, malaria) –cannot penetrate spaces between endothelium  Surface coat: sialic acid residue (-)  galactose moieties exposed – induced phagocytosis

31 Jeanne A Pawitan Spleen –histophysiology Lymphocytes -Ag challenge  white pulp  °B memory cells, plasma cells – lymphoid nodules °T cells (various subcategories) – PALS  marginal sinuses  °Site of Ag challenge °Circulating pool of lymphocytes °Plasma cells Some  stay in marginal zone  Ab  marginal sinuses Most  bone marrow – Ab  bone marrow sinuses

32 Jeanne A Pawitan Tonsils: palatine, pharyngeal, lingual Incompletely encapsulated Aggregates of lymphoid nodules Guard the entrance of oral (oro) pharynx Exposed to °Airborne Ag °Ingested Ag Reaction to Ag °Forming lymphocytes °Mounting immune response

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