Download 9.LYMPHOID TISSUE 120

‫بسم هللا الرحمن الرحيم‬
‫‪LYMPHOID TISSUE‬‬
CELLS OF IMMUNE SYSTEM
1- Lymphocytes:
B cells
T cells: memory, TH1, TH2, TC, TS
Natural Killer Cells.
2- Plasma cells
3- Mast cells
4- Neutrophils
5- Eosinophils
6- Antigen presenting cells
‫ (زيادة عن‬T-LYMPHOCYTES
)‫المقرر‬
• Their plasmalemma has:
1- T cell receptors (TCRs).
2- CD molecules or markers
( cluster of differentiation proteins).
)‫ (زيادة عن المقرر‬T-LYMPHOCYTES
• SUBTYPES:
1- Memory cells.
2- T helper cells:
Are CD4+
TH1 & TH2 cells
3- T cytotoxic cells (Tc cells) (T killer cells)
4- T suppressor cells ( Ts cells).
N.B. Both Tc & Ts cells are CD8+
)‫ (زيادة عن المقرر‬NULL CELLS
1- Natural killer (NK) cells:
are cytotoxic cells.
antibody-dependent cell-mediated cytotoxicity.
are non-B, non-T cells.
are formed in red B.M.
no need for maturation in thymus.
Kill virally altered cells & tumor cells in nonspecific manner.
2- Stem cells.
ANTIGEN PRESENTING CELLS
)‫(المطلوب فقط ما تحته خط‬
1- B lymphocytes.
2- Macrophages.
3- Dendritic cells:
e.g. Follicular dendritic cells,
Interdigitating dendritic cells
Langerhans cells.
4- Epithelial reticular cells of the thymus.
N.B. APCs have class II MHC molecules
(MHC II) but other cells have only MHC I
(‫ )زيادة عن المقرر‬LYMPHOKINES
• Are released by:
1- T helper lymphocytes.
2- Antigen presenting cells.
‫(زيادة عن‬SMALL
LYMPHOCYTES
)‫المقرر‬
‫‪LEUCOCYTES‬‬
‫(زيادة عن المقرر)‬
‫ (زيادة‬DEVELOPMENT OF LYMPHOCYTES
)‫عن المقرر‬
TYPES OF IMMUNE RESPONSE
)‫(زيادة عن المقرر‬
(1) Innate Response:(Fast, non-specific, no memory cells)
By: Neutrophils,
Macrophages,
Mast cells,
NK Cells.
(2) Adaptive response:
a- Humoral immune response
b- Cell-mediated immune response
TYPES OF IMMUNE RESPONSE
)‫(زيادة عن المقرر‬
DC: Dendritic cells
LYMPHOID TISSUE
LYMPHOID TISSUE
A) Diffuse lymphoid tissue
B) Encapsulated lymphoid organs:
1- Lymph nodes.
2- Spleen.
3- Tonsils (are incompletely encapsulated)
4- Thymus.
N.B. Both red bone marrow & Thymus are
considered 1ry. Lymphoid organs.
DIFFUSE LYMPHOID TISSUE
- MALT: lymphocyte infiltration,
solitary lymphoid nodules &
aggregated lymphoid nodules.
- Under the wet epithelial membranes.
- Loose C.T is infiltrated with lymphoid cells
(lymphocytes, plasma cells, macrophages,
reticular cells).
- Lymphoid Nodules
LYMPHOID NODULE
(LYMPHOID FOLLICLE)
• 1ry. : without germinal center
• 2ry. : with germinal center
Bronchial-associated lymphoid
tissue
LYMPHOID NODULE
LYMPH NODES
LYMPH NODE (L.N.)
(A) 1- Capsule
2- Trabeculae (septa)
3- Reticular C.T.
(B) Parenchyma: (lymphoid tissue + lymph sinuses)
1- Cortex
2- Paracortex
3- Medulla
High endothelial venule (postcapillary venule)
CORTEX OF L.N.
1- Lymphatic nodules (follicles):
a- 1ry: without germinal center
b- 2ry: is formed of:
Corona (mantle): Dark, Mostly B-lymphocytes.
Germinal center: Lighter, mostly
activated B-lymphoblasts with macrophages &
dendritic reticular cells.
2- Subcapsular & Cortical (paratrabecular) lymph
sinuses.
PARACORTEX Of L.N.
• It is the thymus-dependent zone of L.N.
• It is composed mostly of T-lymphocytes.
• It contains high endothelial vessels
(postcapillary venules):
- PCV are lined with cuboidal endothelium.
- PCV are the site of entry of lymphocytes
to L.N.
Medulla of lymph node
Medullary Lymph Sinusoids (Sinuses)
MEDULLA OF L.N.
(1) Medullary cords:
are formed mainly of lymphoid cells
( B & T lymphocytes, plasma cells,
macrophages).
(2) Medullary sinusoids ( or medullary sinuses).
N.B. Efferent lymphatic vessels drain lymph with
B & T lymphocytes.
MAIN CELLS OF L.N.
1- B & T lymphocytes.
2- Plasma cells.
3- Macrophages
4- Dendritic reticular cells
FUNCTIONS OF L.N.
• 1- Production of immunocompetent cells.
• 2- Filtration of lymph.
SPLEEN
STROMA OF SPLEEN
1- Capsule: is covered by visceral layer of peritoneum;
mesothelium.
occasionally contains SMCs
2- Trabeculae.
3- Reticular C.T.
PARENCHYMA OF SPLEEN
• (A) White pulp.
• (B) RED PULP.
• (C) Marginal zone.
• N.B. No cortex, no medulla.
No afferent lymphatic vessel.
Splenic microcirculation
Periarterial lymphatic sheath
and the central artery
SPLEEN
Lymphoid nodule with central artery
Lymphoid nodule with central artery
PARENCHYMA OF SPLEEN
(A) White pulp:
1- Periarterial lymphatic sheaths:
housing T lymphocytes.
2- Lymphoid nodules ( with germinal centers):
housing B lymphocytes.
N.B. Both 1&2 have the acentrically located
central artery
SPLEEN
Red pulp:
1) Blood sinusoids
2) Pulp cords
Blood sinusoids of spleen
(B) Red pulp:
1- Pulp (splenic) cords (of Billroth):
Extravasated blood cells, plasma cells,
Macrophages & reticular cells and fibers.
2- Blood sinusoids:
Are lined with elongated fusiform
endothelial cells with large intercellular
spaces & supported by discontinuous,
hoop-like basement membrane.
(C) Marginal zone:
- Between white and red pulps.
- Rich in vascular channels (marginal sinuses),
especially surrounding the lymphoid nodules
- Rich in avidly phagocytic macrophages.
- Contains plasma cells, T & B cells,
macrophages, interdigitating dendritic cells.
- It houses B cells that are specialized to recognize
thymic-independent antigens.
- Site of first entry of B & T lymphocytes from
blood stream to parenchyma of spleen.
FUNCTIONS OF SPLEEN
1- Filtration of blood.
2- Phagocytosis of old RBCs &
old blood platelets & invading
microorganisms.
3- Production & proliferation of
immunocompetent B & T lymphocytes.
4- Production of antibodies.
SPLENIC MICROCIRCULATION
1- Splenic artery
2- Trabecular artery
3- Enter the parenchyma as CENTRAL ARTERY ( in the
white pulp)
4- Enter the red pulp as several straight branches named
PENICILLAR ARTERIES
(pulp arterioles→ Sheathed arterioles→
Terminal arterial capillary)
5- Blood sinusoids
6- Pulp veins
7- Trabecular veins
8- Splenic vein.
Splenic microcirculation
Blood sinusoids of spleen
Tonsils
(1) Palatine Tonsils.
(2) Pharyngeal Tonsil.
(3) Lingual Tonsils.
PALATINE TONSILS
1- Epithelium
2- Tonsillar crypts: 10-12
3- Lymphatic nodules
4- Capsule
PALATINE TONSILS
PHARYNGEAL TONSIL
1- Epithelium
2- Pleats:
Longitudinal infoldings (instead of tonsillar crypts).
3- Lymphatic nodules
& diffuse lymphoid tissue.
4- Capsule.
5- Ducts of seromucous glands.
PHARYNGEAL TONSIL
LINGUAL TONSILS
1- Epithelium.
2- Crypt: a single crypt for each lingual tonsil.
3- Lymphatic nodules.
4- Capsule.
5- Glands: ducts of mucous minor salivary glands open
into the base of a single crypt of each lingual tonsil.
FUNCTION OF TONSILS
Production of antibodies.
THYMUS
THYMUS
A) Stroma:
1-Capsule
2-Interlobular trabeculae: incomplete
B) Thymic lobules:
1-Cortex
2-Medulla
l
CORTEX OF THYMIC LOBULE
A) It contains developing (immature) thymocytes.
98% of thymocytes die?
1-Whose TCRs recognize self-proteins
OR
2-Whose CD4 or CD8 molecules can not
recognize MHC I or MHC II molecules.
B) Epithelial reticular cells
C) Macrophages
CORTEX OF THYMIC LOBULE (cont.)
No lymphatic nodules
No plasma cells
N.B. Tingible body macrophages (resident
macrophages with apoptotic bodies)
MEDULLA OF THYMIC LOBULE
1-Hassall’s (thymic) corpuscles:
-Concentrically arranged epithelial reticular cells in
the medulla.
- Whose number increases with aging.
2-Virgin (naive) mature small T lymphocytes
3- Macrophages
4-Epithelial reticular cells
N.B. Medulla of adjacent thymic lobules are
interconnected- Why? Incomplete trabeculae
BLOOD-THYMUS BARRIER
Site:
It is found in the cortex
Components:
1) Continuous blood capillaries
( The only blood vessel in the cortex)
2) Thick basal lamina
3) Sheath of the epithelial reticular cells
FUNCTION OF THYMUS
Formation, Maturation & Destruction of
T lymphocytes.
Maturation:
Immunoincompetent T cells →→→
Immunocompetent T cells.
General notes about thymus
• No lymphoid nodules
• No reticular fibers
• No sinuses or sinusoids
Development and Involution of the thymus
• It attains its greatest development shortly
after birth
• It involutes after puberty and becomes
infiltrated by adipose tissue
• Remnants of thymus remain in adult to
form T lymphocytes
Involution of Thymus
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