Download 08 organs and tissues_KG 0926

Organization of the lymphoid
organs and tissues
LYMPHOID ORGANS
Primary lymphoid organs:
- Bone marrow
- Thymus
Secondary lymphoid organs:
- Spleen
- Lymphatic vessels
- Lymph nodes
- Adenoids and tonsils
- MALT (Mucosal Associated Lymphoid Tissue)
GALT (Gut Associated Lymphoid Tissue)
BALT (Bronchus Associated Lymphoid Tissue)
SALT (Skin Associated Lymphoid Tissue)
NALT (Nasal Associated Lymphoid Tissue)
Types of endothelium
Primary lymphoid organs
Bone marrow
GENERATION OF BLOOD CELLS DURING LIFE SPAN
BEFORE BIRTH
AFTER BIRTH
Cell number (%)
Yolk sac
80
Flat bones
Liver
60
40
Spleen
20
Tubular bones
0
0 1 2 3 4 5 6 7 8 9
10
20
30
40
50
60
70
years
months
BIRTH
BONE MARROW
TRANSPLANTATION
Structure of the bone marrow
Bone marrow
CELL TYPES OF THE BONE MARROW
Stem cells
Osteoblasts
Stromal cells
BONE
csont
Osteoclasts
B-cell precursors
Progenitors
Precursors
Dendritic cell
Central
centrális
sinus
sinus
Blood circulation
Unspecialized stem cells with unlimited proliferating capacity
SELF RENEWAL AND POTENCY OF DIFFERENTIATION OF STEM CELLS
csont
Stromal
cell
Bone
HSC
Dendritic
cell
HSC – assymetric cell division
self renewal
cell differentiation
Central
sinus
centrális
sinus
CD34+ HSC BONE MARROW
MYELOID
LYMPHOID
CMP
CLP
ERYTHROID
BLOOD CELLS
Endothelial cells
Mesenhymal Stem Cells
(MSC)
Other Stem Cells
Fat
Neuronal cells
Epithelial cells of the liver, kidney, skin,
myocytes of the heart and muscle, GI tract
Bone
Cartilage
Mobilized hematopoetic stem cells (HSC) develop in close contact with
osteoblasts, mesenchymal stem cells (MSC) and endothelial cells
Osteoblast
Nestin+MSC
HSC
MSC
HSC
HSC
HSC
Uccelli A et al. Nat Rev Immunol 2008
BONE MARROW
HSC
MYELOID
PRECURSOR
HEMATOPOIETIC STEM CELL
LYMPHOID
PRECURSOR
BLOOD
BLOOD
DC
monocyte mast neutrophil
TISSUES
DC
THYMUS
macrophage mast neutrophil
B-cell
NK-cell
T-cell
LYMPHOID TISSUES
B-cell
T-cell
Primary lymphoid organs
Thymus
STRUCTURE OF THE THYMUS
Thymocytes from the bone marrow arrive at the thymus and mature into T cells
Capsule
Septum
Blood
circulation
Epithelial cells
Thymocytes
Dendritic cell
Macrophage
Mature naive T- lymphocytes
Hassall’s corpuscle
STRUCTURE OF THE THYMUS
THYMUS INVOLUTION
PERIPHERAL LYMPHOID
ORGANS
Sites of lymphocyte activation
and differentiation
Lymph nodes
Spleen
Epithelial cell – associated lymphoid tissues
MALT (Mucosal Associated Lymphoid Tissue)
GALT (Gut Associated Lymphoid Tissue)
BALT (Bronchus Associated Lymphoid Tissue)
SALT (Skin Associated Lymphoid Tissue)
NALT (Nasal Associated Lymphoid Tissue)
Organization (levels) of immunocytes
Diffuse cells
Follicle
Patch
organ
Lymphatic nodes
Lymphatic vessels
Lymph circulates to the lymph node via afferent lymphatic vessles and then
leaves the lymph node via the efferent lymphatic vessels towards either a more
central lymph node or ultimately for drainage into a central venous sublcavian
blood vessel.
Lymph node
HOMING OF B LYMPHOCYTES IN
LYMPH NODES
Naive B lymphocytes enter lymph nodes
via HEV
B cells are reqruited to HEV from the
blood by CCL21 chemokine secreted by
stromal cells
CCL21 and CCL19 chemokines attract B
lymphocytes to the lymph node
. The spleen filters
the blood and serves
as a secondary
lymphoid organ
Spleen
Lymphocyte aggregations
similar to the lymph node only
that cells and pathogens enter
from the blood
Red pulp- filters the blood; from
antigens, microorganisms and
worn-out RBCs
STRUCTURE OF THE SPLEEN
White pulp
NO LYMPHOID CIRCULATION
Filtration of blood borne antigens
Spleen white pulp
Transverse section
Marginal sinus
B cell corona
Red pulp
Germinal centre
Marginal zone
Periarteriolar lymphocytic
sheath (PALS) – T cell area
Central arteriole
PERIPHERAL LYMPHOID
ORGANS
Sites of lymphocyte activation
and differentiation
Lymph nodes
Spleen
Epithelial cell – associated lymphoid tissues
MALT (Mucosal Associated Lymphoid Tissue)
GALT (Gut Associated Lymphoid Tissue)
BALT (Bronchus Associated Lymphoid Tissue)
SALT (Skin Associated Lymphoid Tissue)
NALT (Nasal Associated Lymphoid Tissue)
Secondary lymphatic tissues
MALT
 Lymphatic tissues that are more diffused are generally known as MALT
(Mucosa associated lymphatic tissue). Similar microanatomy as the lymph
nodes and spleen
• Most of the pathogens get into human body through mucosa
• A thin, huge surface, dinamic structure
• Intense and active immune surveillance mechanisms ensure the protection
• Mucus contains glycoproteins, proteoglycans, special enzymes
• Anti microbial peptides provide biological defence mecanism against
intection
• Most of the lymphocyte reside arround the mucosal surface
Gut-associated lymphoid tissues
Gut-associated lymphoid tissues
Peyer’s patches 5-100 follicles forming a dome structure
M-cells: microfold cells --- no glycocalyx – antigen uptake
GALT
• The Lamina propria contains lymphatic tissue
underlying the gastrointestinal tract connective tissue
• The small intestine contains lymphoid nodules; the
Peyer’s patches and isolated lymphoid follicles.
• Pathogens are delivered across the mucosa to APCs by
specialized mucosal epithelial cells are called the M
cells (microfold cells).
Transport of antigens via M cells
Dendritic cells of the lamina propria outside Peyer’s patches
capture antigens by sampling the gut lumen directly
Intra-epithelial lymphocytes
GALT
• The large intestine contains isolated lymphoid
follicles and the appendix
• Antigens arising from Peyer’s patches and Lamina Propria travel to T cell areas in
the GALT or Mesenteric lymph nodes.
NALT
 Guarding the gastrointestinal entrance
  Waldeyer’s ring: Pharyngeal, Tubal, Palatine and Lingual Tonsils
Tonsilitis
Cellular components of the cutaneous immune system