Transcript a. T-lymphocytes

Chapter 8
Lymphoid organs
General organization of lymphoid organ:
•
largely consist of lymphoid tissue
Reticular tissue: stellate-shaped with processes to form
network
•
Diffuse lymphoid tissue
Lymphoid nodules
Cells:
Lymphocyte (chiefly)
Plasma cell
antigen presenting cell
other cells
a. Diffuse lymphoid tissue:
• no clear boundary
• mainly consists of T-lymphocyte
• postcapillary venules:
-high endothelial venules, lining of
tall cuboidal cells
-opening for lymphocyte enter
lymphoid tissue from blood
Lymphoid
nodule
Diffuse LT
b. Lymphoid nodule:
• spherical or ovoid
• have clear boundaries
• mainly composed of B-
•
lymphocyte
germinal center: lighterstained central zone, these
cells produce antibodysynthesizing plasma cells
Cells of lymphatic tissue
1) Lymphocyte:
a. T-lymphocytes:
• cytotoxic T cell: Tc C- kill the tumor cell, virus
infective cell and foreign cell
• helper T cell: Th C- stimulate the Blymphocyte differentiate into plasma cell
• suppressor T cell: Ts C – regulate the function
of B-lymphocyte and T-lymphocyte
b. B-lymphocytes: become into plasma cell
c. NK cell: attack virus infective cell and tumor
cell without previous stimulation
2) Plasma cell
3) Antigen presenting cell:
a. dendritic cell
b.macrophage
Antigen processing is a necessary preliminary step for
activation of T cell.
4) other cells:
• granulated cell
• mast cell
• blood platelet
• blood-bone stem cell
Function:
i.
immunologic defense
ii. immune surveillance
iii. immune homeostasis
Lymphatic organs:
central lymphatic organs:
produce the lymphocyte
antigen-independent proliferation
contain: thymus---T-lymphocyte
bone marrow---B-lymphocyte
peripheral lymphatic organs:
receive the lymphocyte and perform the immune
response
antigen-dependent proliferation
contain: lymph node
spleen
tonsils
The immune system:
• consists of the lymphatic organs, lymphocytes of the blood
and lymph, and collections of different types of lymphocytes
dispersed throughout the connective tissue.
• is essential to the body’s immunological defense against
bacteria, viruses and other foreign bodies.
Immune response:
•Cellular immunity: involving mainly T-lymphocytes
•Humoral immunity: involving mainly B-lymphocytes
•Mast cells, macrophages and other white blood cells are also
involved in the immune response.
thymus
•
•
•
A flattened, bi-lobed structure lying in the
superior mediastinum
In the new-born child it is at its greatest size
relative to body size
Thymus continue to grow until puberty when it
is replaced by fibrofatty tissue
Structure:
 Capsule ( C.T.)
interlobular septa (trabecula)
Endothelial reticular cell (ERC)
 Cortex:
Lymphocyte: thymocyte
Macrophage: secrete IL-1
ERC
Lymphocyte: few
 Medulla:
Macrophage: secrete IL-1
Thymic corpuscles
Thymus
Cortex
medulla
The cortex of thymus
A very active site of lymphocyte production
More than 90% of the thymocyte degenerate in this area,
only less than 10% of thymocyte will mature and leave the
thymus as T-lymphocytes through the postcapillary venules.
Endothelial reticular
cell (ERC)
The medulla of thymus
Hassall’s ( thymic) corpuscles
• a characteristic feature of the thymus
• their significance is as yet unknown
Hassall’s ( thymic) corpuscles
spherical or ovoid body, 20-150um in diameter,
composed of concentrically-arranged epithelial
reticular cells, the central cells often show
degeneration
Blood-thymus barrier:
provide a stable environment for lymphocytes developing
in the cortex---prevents circular antigens from reaching the
thymic cortex where T cells are being formed
Consists of :
endothelial cell of continuous
capillary
very thick basement
membrane
perivascular space with
macrophage in it
basement membrane of ERC
ERC or their processes with
desmosome
Thymus function:
 the thymic epithelial reticular cells can secrete thymic
hormones (thymosin, thymolin, thymopoietin)
 induce the stem cell to differentiate into
T-lymphocyte
Adult thymus has high infiltration of adipose tissue (A)
Older adult thymus has large amounts of adipose tissue
Lymph node
• A mass of lymphatic tissue enclosed in a capsule of
•
•
connective tissue
Widely scattered along the course of lymph vessels
Concentrated in area in neck, axilla (arm pits),
and groin.
Structure
---capsule: CT, trabeculae or septa
---cortex: outer densely-stained part
---medulla: inner paler-stained part
hilum
Structure:
 capsule
trabecula
several afferent lymph vessels,
 cortex
out cortex:
(superficial cortex)
lymphoid nodule (B-LC)
inner cortex:
(paracortical zone)
diffuse lymphoid tissue (T-LC)
cortical lymphatic
sinuses
internodule zone
subcapsular sinus:
peritrabecular sinus
macrophage
capsule
outer cortex
inner cortex
SS: subcapsular sinus
T: trabecular
Capsule
Subcapsular
sinuses
Trabeculae
Afferent lymph vessels
GC
Postcapillary venules in inner cortex
Medulla
---medullary cord:
LT cord:
• B-lymphocyte, plasma
cell, macrophage, mast
cell
---medullary sinus:
• similar to cortical
sinus and connect with
them
• more macrophage
capsule
outer cortex
inner cortex
Passage of lymph in lymph node
Afferent lymph vessels
Subcapsular sinus
Cortical sinuses
Medullary sinuses
Efferent lymph vessels
Lymph enters afferent lymph vessels passes through subcapsular
sinuses and down through trabecular sinuses around trabeculae.
Efferent lymph vessels in hilum
Recirculation of lymphocytes:
Lymphoid tissue
Postcapillary
venules
Efferent lymphatic vessel
Blood circulation
Functions of lymph node
• Filter the lymph
• Place to perform the immune response
• Involve in the recirculation of
lymphocyte
Spleen
 located in the passages of blood
capsule
 structure
parenchyma
white pulp
red pulp
marginal zone
Structure:
 capsule:
D.C.T. containing smooth muscle----trabecular; capsule is
covered by mesothelium
The splenic artery branch into trabecular arteries
White pulp:
• gray-white spots
• periarterial lymphatic sheath:
- diffuse lymphoid tissue : T-lymphocyte,
macrophage
- central artery
• splenic corpuscle:
-lymphoid nodules: B-lymphocyte, macrophage
splenic corpuscle
Marginal zone:
•
•
•
•
between White pulp and Red pulp
T-, B-lymphocyte, macrophage, less erythrocyte
marginal sinus: central artery’s branch- channel for
antigen and lymphocyte enter lymphoid tissue
function: first capture, recognize antigen and induce
immune reaction
Red pulp:
splenic cord:
• Lymph tissue cord
• B-,T-lymphocyte, macrophage, erythrocytes
• function: filter blood
splenic cord
splenic sinus
splenic sinus:
Blood sinus; 12-14um
endothelial cell: rod-liked, gap
Reticular fiber
basal lamina: incomplete
Abundant macrophage
splenic sinus
splenic cord
endothelial cell
Blood supply of spleen
Study by yourself
splenic A→trabecular A→central A
branches → marginal sinuses →
penicillar arterioles (including: pulp arteriole→
sheathed capillary→ arterial capillary) →
splenic sinus→ pulp venule→ trabecular vein→
splenic vein
Function:
a. filter the blood
b. immunological defence
c. production of blood cells in fetus
d. blood storage: 40 ml
5. Tonsil
(Study by yourself)
---palatine tonsil
---pharyngeal tonsil
---lingual tonsil
structure
 Mucosa
stratified squamous epithelium
Epithelium
form crypts
lymphocyte infiltration
Lamina propria
lymphatic nodules
diffuse lymphatic tissue
 Capsule: C.T.
Tonsil
Mononuclear phagocyte system
(Study by yourself)
monocyte
young monocyte
Bone marrow
Tissues or
organs
Blood
CT: macrophage
Liver: Kuffer cell
Lung: dust cell
Nerve tissue: microglia
Osseous tissue: osteoclast
Skin: Langerhans cell
Function of MPS:
 phagocytosis
 participate in immune reaction
 secrete bioactive substances