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Histology of the immune (lymphoid, lymphatic) system

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Presentation on theme: "Histology of the immune (lymphoid, lymphatic) system"— Presentation transcript:

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

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

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

4 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 Jeanne A Pawitan

5 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 Jeanne A Pawitan

6 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) Jeanne A Pawitan

7 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 – 5th month prenatal LM: vascular compartment (A., V., sinusoids) Intervening spaces hemopoietic compartments – meshwork - islands of hemopoietic cells Adventitial reticular cells, reticular fibers Jeanne A Pawitan

8 Bone marrow cells Hemopoietic cells Adventitial reticular 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 Jeanne A Pawitan

9 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) Jeanne A Pawitan

10 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 Jeanne A Pawitan

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

12 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. Jeanne A Pawitan

13 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 Jeanne A Pawitan

14 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 Jeanne A Pawitan

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

16 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 Jeanne A Pawitan

17 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 Jeanne A Pawitan

18 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 Jeanne A Pawitan

19 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 Jeanne A Pawitan

20 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 Jeanne A Pawitan

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

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

23 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 Jeanne A Pawitan

24 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 Jeanne A Pawitan

25 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) Jeanne A Pawitan

26 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 Jeanne A Pawitan

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

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

29 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 >< platelet reaction to coll >< coagulation Macrophages particularly numerous near sinusoids Jeanne A Pawitan

30 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 Jeanne A Pawitan

31 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 Jeanne A Pawitan

32 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 Jeanne A Pawitan

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