Immune organs
and tissues
Shijie Sun (Associate Prof.)
Department of Immunology, DMU
KEY POINTS:
• To master:
– The components of human immune organs and tissues,
and their functions
• To be familiar with:
– The function of MALT
• To understand:
– Lymphocyte homing; lymphocyte recirculation
Basic Components of the Immune System
Immune organs
Immune cells
Immune molecules
Basic Components of the Immune System
Immune organs
Central
lymphoid organ
Peripheral
lymphoid organ
bone marrow
spleen
thymus
lymphoid nodes
MALT
Immune cells
Immune molecules
Membranous
Stem cell
Lymphocyte
Monocyte
macrophage
Dendritic cells
mononuclear
Other cell
Granulocytes
Mast cell
Platelets
Erythrocyte
TCR
BCR
CD Molecule
MHC
Adhesion
molecule
secretory
Ig
Complement
cytokine
Central (primary) lymphoid organs
bone marrow, thymus
To provide a microenvironment
necessary for lymphocytes
maturation.
Peripheral (secondary) lymphoid organs
To trap antigen and provide sites for
mature lymphocytes to interact with
that antigen.
Spleen,lymph nodes,MALT
1. Central (primary) lymphoid organs
(1) Bone Marrow
Function : microenvironment for
i the developing of blood cells and immune cells
ii B cell and NK cell maturation
iii humoral immune response
Self-renewing stem cell
Lymphoid progenitor
Myeloid progenitor
Pluripotent stem cell
Natural killer
(NK) cell
B lymphocyte
T lymphocyte
Erythroid CFU Megakaryocyte Basophil CFU Eosinophil CFU Granulocyte-monocyte CFU
Erythrocytes
Platelets
Basophils
Eosinophils
Neutrophils monocyte
Hematopoietic inductive microenvironment, HIM
1. Stromal cells, such as macrophage, fibroblasts,
reticular cell, endothelial cells.
2. Hematopoietic growth
IL3,4,6,7,SCF, GM-CSF,etc.
factors, including
3. Extracellular matrix:
Function:
To provide environment for hematopoiesis and
regulate cell survival, proliferation, differentiation
and trafficking.
Case 1. SCID
Q1: Why could the bone marrow transplantation treat SCID?
Q2: How to find the suitable donor?
Q3: Would you like to be a volunteer to donate your BM or stem cells?
(2) Thymus
Cortex：
outer compartment, is densely packed
with immature T cells, called thymocytes.
Medulla：
inner compartment, is sparsely
populated with thymocytes.
Function：
To secrete various hormones; promote
the differentiation of thymocytes.
DN cell
Cortex
cortical
epithelial cell
DP cell
macrophage
Dendritic cell
Medulla
cell
SP cell
cell
medullary
epithelial cell
Enter peripheral lymphoid tissues and organs
T cells differentiate in thymus
Athymic nude mice (Foxn1nu)
a nature animal model
for T cell selective deficiency
Athymic nude mice are kept behind a barrier with HEPA filtered
air, autoclaved fee, bedding, water and cages. A research
assistant uses aseptic procedures to protect these mice from
organisms in the environment.
DiGeorge Syndrome
This disorder typically results
from various deletions in a
region on chromosome
22q11.2 containing up to 50
genes, with the T-box
transcription factor (TBX1)
thought to be most influential.
Q: could the Digeorge syndrome be
treated with bone marrow
transplantation?
2 Peripheral (Secondary) lymphoid organ
Lymph nodes
Spleen
Mucosa-associated lymphoid tissue (MALT)
Generative lymphoid organs
Peripheral lymphoid organs
Recirculation
blood
B
Bone marrow stem cell lymphocytes
lineage
Bone
marrow
Lymph node
Spleen
Mucosal and
cutaneous
lymphoid tissues
Mature
B lymphocytes
T
lymphocytes
lineage
Blood,
lymph
Thymus
Mature
T lymphocytes
Recirculation
Maturation of lymphocytes
(1) Lymph nodes
Structure of lymph nodes
Cortex
cortex：
B cell riched zone
paracortex：
T cell riched zone、
HEV
Medulla
Function of lymph nodes
1. Home for mature T/B lymphocytes
T： 75%， B： 25%
2. Main site for adaptive immune response
DC， FDC
3. Lymphocyte recirculation
4. Physical and biologic filters: Mφ
(2) Spleen
Structure of spleen
T cell zone
HE
(IHC)
B cell zone
(IHC)
Function of spleen:
1. Home for T/B lymphocytes
B： 60% ， T： 40%
2. Main site for adaptive immune response
3. Synthesize some complement components
4. Physical and biologic filter
(3) Mucosa-associated lymphoid tissue
(MALT) or mucosal immune system (MIS）
The organized and diffuse lymphoid tissues
found in submucosal regions of the body,
such as alimentary, genitourinary and
respiratory tracts.
For example: tonsils, Peyer’s patches,
vermiform appendix ,etc.
A solitary lymphoid nodule
in the large intestine. This
nodule is localized in the
mucosa and submucosa of
the intestinal wall.
1.Appendix of a 10 year old
2.Appendix from a 36-year old
man
Secrete antibodies across
the mucosal surface
Local (mucosal) immunity
Immune response in intestinal lymph system
sIgA
Mucosal epithelium M cell
Macrophage
IgA
Th
B
Plasma cell
3 Recirculation of lymphocytes
Homing : primary →→→secondary
Recirculation : secondary →→→secondary
secondary →→→tissue
Native
T cell
Lymph node
without antigen
Blood
vessel
Activated
T cell
High
endothelial
venule
Peripheral tissue site of
infection/inflammation
microbes
Efferent lymphatic vessel
Lymph node
with antigen
Afferent
lymphatic
vessel
Lymphatic
vessel
Peripheral
blood vessel
Efferent
lymphatic
vessel
Thoracic duct
Pathways of T lymphocyte recirculation
Summary
Quiz:
Q: All blood cells in an adult human can trace their ancestry
to which compartment within the body?
A.Thymus
B.Bone marrow
C.Lymph node
D.Peyer's patch
E.None of the above
Quiz:
Q: All blood cells in an adult human can trace their ancestry
to which compartment within the body?
A.Thymus
B.Bone marrow
C.Lymph node
D.Peyer's patch
E.None of the above
A: B
Quiz:
Q: Which of the following is NOT considered as primary
lymphoid tissue?
A.Draining lymph node
B.Thymus
C.Peyer's patch
D.Choices A and C are not primary lymphoid tissue.
E.None of the above is primary lymphoid tissue.
Quiz:
Q: Which of the following is NOT considered as primary
lymphoid tissue?
A.Draining lymph node
B.Thymus
C.Peyer's patch
D.Choices A and C are not primary lymphoid tissue.
E.None of the above is primary lymphoid tissue.
A: D
Case 1. SCID
Q1: Why could the bone marrow transplantation treat SCID?
Q2: How to find the suitable donor?
Q3: Would you like to be a volunteer to donate your BM or stem cells?
Case 2.
Elizabeth Bennet was born with a low body weight of 2.1 kg, and
dysmorphic facial features were noted, including low-set ears as
well as a relatively small mouth with an undersized lower jaw
(micrognathia) . At 2 days of life, Elizabeth developed feeding
difficulties, rapid breathing, increased fatigue, and a bluish
discoloration of the skin. At 4 days of age, Elizabeth developed
seizures. She was found to have very low blood levels of calcium
(6.2 mg dl–1, normal 8.5–10.2 mg dl–1) and was treated with calcium
and vitamin D. With the help of fluorescence in situ hybridization
(FISH), she was found to have a deletion of the chromosomal region
22q11.2 on one of her two copies of chromosome 22, consistent
with a diagnosis of DiGeorge syndrome.
Questions:
• Would bone marrow transplantation work in patients
with DiGeorge syndrome?
• What could be the reason that patients with DiGeorge
syndrome are at higher risk of autoimmune
manifestations?
thank you for your attention