Transcript ORGANS OF THE IMMUNE SYSTEM LYMPHOID ORGANS

ORGANIZATION AND STRUCTURE OF THE
IMMUNE SYSTEM
ORGANS OF THE IMMUNE SYSTEM
LYMPHOID ORGANS
GENERATION AND MIGRATION OF CELLS OF THE
IMMUNE SYSTEM
LYMPHOCYTE HOEMOSTASIS, RECIRCULATION
THE ROLE OF LYMPHATICS IN THE TRANSPORTATION
OF ANTIGENS
INITIATION OF IMMUNE RESPONSE IN PERIPHERAL
LYMPHOID ORGANS
ORGANIZATION OF THE IMMUNE SYSTEM
LYMPHOCYTES CONGREGATE IN SPECIALIZED TISSUES
•
CENTRAL (PRIMARY) LYMPHOID ORGANS
– Bone marrow
– Thymus
DEVELOPMENT TO THE STAGE OF ANTIGEN RECOGNITION
•
PERIPHERAL (SECONDARY) LYMPHOID ORGANS
– Spleen
– Lymph nodes
– Skin-associated lymphoid tissue (SALT)
– Mucosa-associated lymphoid tissue (MALT)
– Gut-associated lymphoid tissue (GALT)
– Bronchial tract-associated lymphoid tissue (BALT)
ACTIVATION AND DIFFERENTIATION TO EFFECTOR CELLS
•
BLOOD AND LYMPH CIRCULATION
– Lymphatics
– collect leaking plasma (interstitial fluid) in
connective tissues
– Lymph
– cells and fluid
– No pump
– one way valves ensure direction – edema
– Several liters (3 – 5) of lymph gets back to the blood daily – vena cava
superior
GENERATION OF BLOOD CELLS
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
ORGANIZATION OF THE IMMUNE SYSTEM
T-lymphocytes
Pathogens
Allergens
Lymph nodes
Blood circulation
Lymph circulation
Cellular
immune response
Thymus Helper Th
Cytotoxic Tc
Spleen
PERIPHERAL
SECONDARY
LYMPHOID
ORGANS
WALDEYER RING
Tonsils, adenoids
Palatinal, pharyngeal
lingual and tubar tonsils
Antigens
Nyirokerek
Lymphatic
vessels
Bone
marrow
CENTRAL
PRIMARY
LYMPHOID
ORGANS
Stem cells
B-lymphocytes
Antibodies
THE BONE MARROW
HSC cell: assymetric division
7-8000/day
self renewal
Stromal cell
Stem cell
Bone
csont
B-cell precursors
B-precursor
2-3x108
Pre-B
2-3x107
B-cell
1-3x106
Dendritic cell
2x107
T cell precursors
migrating to the thymus
Central
centrális
sinus
sinus
Mature naive
B-lymphocytes
STEM CELLS
Unspecialized cells with unlimited
proliferating capacity
CHARACTERISTICS
SELF RENEWAL
ASSIMMETRIC DIVISION
Self renewal
+
Assimmmetric division
At least one differentiated cell
Precursor/progenitor
Or more differentiated cell
Precursor/progenitor
Scheme of B Cell Development in the Bone Marrow
Progenitors
E
n
d
o
o
s
t
e
u
m
Stromal cells
Pre-B
X
X
X
Macrophage
Immature &
mature B
Central
Sinus
BONE MARROW
HSC
MYELOID
PRECURSOR
HEMATOPOIETIC STEM CELL
LYMPHOID
PRECURSOR
BLOOD
BLOOD
DC
monocyte mast neutrophil
TISSUES
DC
THYMUS
mackrophage mast neutrophil
B-cell
NK-cell
T-cell
LYMPHOID TISSUES
B-cell
T-cell
STRUCTURE OF THE THYMUS
Capsule
Septum
Blood
circulation
Epithelial cells
Thymocytes
Dendritic cell
Macrophage
Mature naive T- lymphocytes
Hassal’s corpuscle
THYMUS INVOLUTION
•Up to puberty/adolescence the size of the thymus is increasing and naive T
lymphocytes are produced in waves to ensure protective immune responses
•A sustained loss of tissue mass, cellularity and functionality of the thymus starts
after puberty and lasts to middle age followed by a slower rate of involution
extending to old age
•DN cells do not proliferate and differentiate
•Diversity of the TCR repertoire progressively becomes more limited
•The thymic tissue is replaced by fat deposits
•In old people naive peripheral T cells proliferate more extensively than those in
younger individuals to compensate low cell numbers and reach their replicative limits
earlier than in young people
REDUCED RESISTANCE TO INFECTION AND TUMORIGENESIS
Similar number of T cell progenitors to young individuals
Limited IL-7 production, Bcl-2 expression and TCRβ rearrangement
Replicative potential of thymic stromal cells is decreased
The levels of nerve growth factor (NGF) secreted by medullary thymic epitelial cells
(TEC) and IGF-1 produced by thymic macrophages decline