Download Immune - lymphatic system

Immune system - organisation:
Immune - lymphatic system
♣ organised lymphoid structures
♣ cell components
- histology & embryology
← lymphocytes
event. lymphatic follicles
← accessory cells
♦monocytes-macrophages system♦
Immune defense:
Immune response:
INNATE IMMUNITY
- surface protective system
- blood proteins: complement system
- phagocytic cells, NK cells
ADAPTIVE IMMUNITY
- humoral
- cell-mediated
• The ability to distinguish „self“ a „nonself“
→ immune defence
x
immunodeficiency
→ autotolerance
x autoimmune diseases
→ immune supervision
x hypersensitivity
Lymphoid organs
Primary:
• bone marrow
• thymus
Secondary:
• spleen (lien)
• lymph nodes (nodi lymphatici)
• tonsils
• diffuse lymphatic tissue in the mucosa
of some systems (GALT, BALT)
Structure of a lymph node
• convex face - „afferent“
• concave hilum - „efferent“
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•
•
•
capsule => trabecule
outer cortex
inner cortex (paracortical layer)
medulla
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Lymph node (HE 8x)
Lymph node - capsule (HE 128x)
Lymph node - cortex
• subcapsular sinus → intermediate sinuses
• LYMPHATIC NODULE:
ℵ PRIMARY
ℵ SECUNDARY:
- germinal centre
- mantle zone
- marginal zone
Lymphatic nodule (HE 50x)
Lymph node - paracortex
•
•
•
•
T- lymphocytes (CD4+)
APC (antigen presenting cells)
macrophages
reticular cells
• high endothelial venules (HEVs)
Lymph node - medulla
• medullary CORDS
– B-lymphocytes and plasmocytes
– APC
• medullary SINUSES
– lining of the reticular cells and macrophages
– reticular fibres over the sinuses=> network
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Lymph node - medulla (HE 20x)
Tonsils
= accumulated lymphatic tissue under the epithelium
without continuous sheath
function: lymphocytes production
Waldayer`s circle:
•
tonsilla lingualis
•
tonsillae palatinae
•
tonsilla tubaria
•
tonsilla pharyngea
Tonsilla palatina
(HE 6x)
Aggregates of lymphocytes&APC
= lymphoid follicles of the same structure as
the lymphatic nodules
e.g.
• Peyer`s patches
• appendix - „ tonsilla abdominalis“
Spleen
= the largest sec. lymphoid organ (150g)
• immune filter of the blood
• erythrocytes destruction
• Ab production
The development of the spleen
• from 5th week
• derived from mesenchym in dorsal mesogastrium
• mesenchymal cells are differentiated in ⇒
– capsule
– connective tissue net
– parenchyma
• in 4th month - hematopoesis
• from 2nd month - white blood cells forming
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Structure of the spleen
• CAPSULE of connective tissue:
– collagen fibres, some smooth muscle cells,
– covered by tunica serosa (except hilum)
– irradiate connective trabeculae lienalis
• STROMA composed of reticular fibres
• RED PULP
• MARGINAL ZONE
• WHITE PULP
Vascularisation of the spleen
elastic fib
• aa. trabeculares
• aa. centrales in PALS
= > sinuses of the marginal zone
• aa. penicillatae
=> splenic sinusoids - closed circulation
=> red pulp
- open circulation
• ….….venae trabeculares, vena lienalis
White pulp
← PALS surrounds the central artery
– T-lymphocytes
← germinal centres of the lymphatic nodule
– B-lymphocytes
←marginal zone (corona)
– vascular sinuses a lymphatic tissue
Red pulp
• splenic sinusoids
– elongated endothelial cells, incoherent BM
– surrounded by the reticular fibres
• cords of Billroth
← lymphocytes, macrophages, reticular cells,
erythrocytes ....
+ reticular tissue
♦ APC, B-cells
Thymus
= central lymphoid organ
• relatively largest in birth (12-14g)
• after puberty begins to involute
• some remnants in adult
The development of the thymus
• cortical epithelial cells ← ectodermal 3th
branchial cleft
• medullary epithelial cells ← endodermal 3th
pharyngeal pouch
♣ 10th week - colonisation by the lymphocytes
← from the blood islets, the liver and bone marrow
♣ maturation of T-cells in immunocompetent cells
→ into lymph nodes, spleen etc.
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The structure
of the thymus
(HE 15x)
• capsule
→ trabeculae
• cortex thymi
• medulla thymi
The medulla of the thymus
• epithelial cells of endodermic origin
Cortex of the thymus
• epithelial cells
= star-like cells joined by desmosomes
=> network
• many small thymocytes
– mostly T-lymphocytes
– many mitosis
• macrophages
• large T-lymphocytes
Medulla
(HE 480x)
• thymocytes (small and medial)
• fully mature T-cells
• macrophages
• Hassall`s corpuscles (30-150 um)
The vascularisation of the thymus
Histophysiology of the thymus
• continuous capillaries
• functional blood-thymus barrier
– endothelium & basal lamina
– pericytes
– some connective tissue (+ macrophages)
– epithelial cells
• T-cells increase
– carried by the blood
– into nodes, spleen, Peyer` s patches etc.
• in the medulla more developed than in cortex
• DiGeorge syndrome - aplasia of the thymus
• grow factors production
proliferation a differentiation)
(T-cells
• corticoids and steroid hormones attenuate the
proliferation, accelerate the involution
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