Download T cells

Chapter III
General introduction of immune system
Immune system
immune organs or tissues
bone marrow
thymus
spleen
lymph nodes
Immune cells :
lymphocytes : T cells , B cells and NK cells
phagocytes: Dendritic cells ,macrophage ,PMN
immune molecules :
antibody
complement (补体）
cytokines
adhesive molecules
Immune organs


Central immune organs or primary lymphoid organs
The site that lymphocytes generate and mature into
functional cells
Bone marrow and Thymus
Peripheral immune organs or secondary lymphoid
organs and tissues
The sites that T and B lymphocytes reside in and
respond to antigens
spleen , lymph nodes , mucosal or cutaneous
lymphoid tissues
Section I Central immune organs
I. Bone marrow
1. The bone marrow is the site of generation of all
circulating blood cells in the adult, including
immature lymphocytes
2. The bone marrow is the site of B cell maturation
3. The sites that secondary humoral
immunity carries through
II. Thymus
1. The structure of thymus
Cortex
outer cortex : immature T cells ( thymus cells)
inter cortex : thymus epithelial cell, macrophage , DC
Medulla
Mature T cells + thymus epithelial cell, macrophage , DC
The structure of thymus
2. The function of thymus

The thymus is the site of T cell maturation

Immune regulation:
Secrete cytokine and thymulin-like molecules
Thymosin（胸腺素），
thymulin-（胸腺刺激素）
thymopoietin（胸腺生成素）
To promote the proliferation , differentiation of
thymocytes
Section II
Peripheral Immune tissues and organs

The immune organs /tissues or secondary lymphoid
organs/tissues are sites that T and B lymphocytes reside
in and respond to antigens
spleen
lymphoid nodes
mucosal immune system
(mucosal or cutaneous-associated lymphoid tissues,
MALT,)
I. Spleen
1. The Structure of spleen
white pulp
Central arteriole
peripheral lymphoid sheaths (PALS)
T–cell area : around the central arteriole
contain T cells , dendritic and macrophage
B -cell area: lymphoid follicles
contain B cells and macrophage and dendritic cells
primary lymphoid follicle
secondary lymphoid follicle
 Red pulp:
cellular cords : B cells , plasma cells and macrophage ,DC
venous: blood

2. Function of spleen




The site of T and B cells residence
B cells : thymus-independent area
T cells : Thymus –dependent area
Site of immune response to antigens
Synthesize some bioactive substance
component of complement
Filtering blood
II. Lymphoid nodes
Structure of Lymphoid node
Cortex :
Outer cortex: thymus-independent area : B cell-rich area
lymphoid follicle/lymphoid nodule :
primary lymphoid follicle : without germinal center
mature and naïve B cells
secondary lymphoid follicle : with germinal center
activated B cells and memory B cells and macrophage
Paracortex : T cell-rich area+ dendritic cells
post-capillary venules, PCV or high endothelial venules
Medulla :
medulla cords: macrophage and plasma cells
medulla sinus
2. Function of lymphoid node

The site of T and B cells residence
B cells : thymus-independent area
T cells : Thymus –dependent area

Site of immune response to antigens

Part of Recirculation of lymphocytes

Filtering blood
III. Skin and mucosal immune system

Skin-associated lymphoid tissue

Mucosal immune system, also named as
mucosa-associated lymphoid tissue, MALT) is
in the epithelia , lamina propria and submucosal
area of gastrointestinal, respiratory and
genitourinary tract
（I）The constitution of MALT



Gut-associated lymphoid tissue, GALT
Nasal-associated lymphoid tissue, NALT
tonsils
Bronchial-associated lymphoid tissue,
BALT : nodule
Gut-associated lymphoid tissue, GALT
(1) mucosa
Epithelia:
intraepithelial lymphocytes (IEL) : T cells
M cells
lamina propria:
lymphoid nodule
aggregated lymphoid nodule or Peyer’s patches:
B cells and T cells
solitary lymphoid nodule: B cells and T cells
(2) submucosa
Scattered lymphoid tissues : T cells
intraepithelial lymphocytes (IEL) : T cells
In mice :
40-50% of lymphocytes come from thymus ,  T cells
50-60% of lymphocytes come from non-thymus
( from bone marrow) ,  T cells
M cells :
•Some of the epithelial cells overlying Peyer’s Patches are
specialized membranous( M ) cells.
• M cells lack microvilli,are actively pinocytic, and transport
macromolecules from the intestinal lumen into subepithelial
tissues.
•They are thought to play an important role in delivering antigen
to Peyer’s patches
submucosa
CD4+ large intestine IEL in mice
with GVHD
positive percent
30
normal
control
GVHD
20
10
0
CD4+ T
CD4+  T
n=3

CD4+  T
graft contral
CD4/CD8
normal
CD4/CD8
 T receptor
 T receptor
SGVHD
（II）The function and features of MALT



First defense line
Site of immune response to antigens
Secrete sIgA
Section III Lymphocytes homing and recirculation
I. Lymphocyte homing
The process by which particular subsets of
lymphocytes selectively enter some tissues
but not others is called lymphocyte homing
II. lymphocyte recirculation
The continuous movement of lymphocytes
between blood stream and peripheral
lymphoid tissues is called lymphocyte
recirculation
1. Pathway of lymphocyte recirculation
2. Significance of lymphocyte recirculation
Lymphoid node-blood recirculation



Blood
Enter into paracortex of Lymphoid node by high
endothelial venules (HEV) in
efferent lymphatics
venule
Thoracic duct
Spleen-Blood recirculation



Blood
Enter into white pulp of spleen via
central artery
spleen venule
Tissue –lymphoid node-blood recirculation
Tissues
Afferent lymphatics
Lymphoid node
efferent lymphatics
Blood
Significance of lymphocyte recirculation

Renew the lymphocytes in peripheral lymphoid
organs

Maximize the chances of specific encounter with
antigen and initiation of adaptive immunity

Enable lymphocytes to lymphoid tissue throughout
body and facilitate immune response to antigen
Review
1.Terms
MALT, Central immune organs, Peripheral immune
organs, lymphocyte recirculation, Lymphocyte
homing
2. Questions :
Significance of lymphocyte recirculation
The function of thymus, bone marrow, spleen , LN and
MALT