chapter iii general introduction of immune system
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Chapter III General introduction of immune system
Immune systemImmune system immune organs or tissuesimmune organs or tissues bone marrow bone marrow thymus thymus spleenspleen lymph nodeslymph nodes Immune cellsImmune cells : : lymphocytes : T cells , B cells and NK cellslymphocytes : T cells , B cells and NK cells phagocytes: Dendritic cells ,macrophage ,PMN phagocytes: Dendritic cells ,macrophage ,PMN immune moleculesimmune molecules : : antibodyantibody complement complement (( 补体)补体) cytokines cytokines adhesive moleculesadhesive molecules
Immune organs Central immune organs or primary lymphoid organs The site that lymphocytes generate and mature into fun
ctional cells Bone marrow and Thymus Peripheral immune organs or secondary lymphoid or
gans and tissues The sites that T and B lymphocytes reside in and respo
nd 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 , DCMedulla 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 thym
ocytes
Section II
Peripheral Immune tissues and organs
The immune organs /tissues or secondary lymphoid orga
ns/tissues are sites that T and B lymphocytes reside in an
d respond to antigens
spleen
lymphoid nodes
mucosal immune system
(mucosal or cutaneous-associated lymphoid tissues, M
ALT,)
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 mucos
a-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 micewith GVHD
CD4+ T CD4+ T CD4+ T0
10
20
30
normalcontrolGVHD
n=3po
sitiv
e pe
rcen
t
CD
4+
normal graft contral SGVHD
T receptor
CD
4/C
D8
CD
4/C
D8
T receptor
( 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
Blood Enter into paracortex of Lymphoid node by hi
gh endothelial venules (HEV) in
efferent lymphatics Thoracic duct venule
Lymphoid node-blood recirculation
Spleen-Blood recirculation
Blood Enter into white pulp of spleen via cen
tral 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
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