Download Chapter 8 Immune Organs

Chapter 3
Immune System
Chapter 3 Immune
System (Is)
 Immune organs and immune tissues
Central immune organs(primary lymphoid organs)
Peripheral immune organ(secondary lymphoid organs)
 Immunocytes
Lymphocytes(T,B cells and NK cells)
APC(Mɸ,DC,B cells)
Other cells(neutrophil,basophil,eosinophil etc.)
 Immune molecules
Antibody,Complement,Cytokine
CD and adhesion molecules,MHC molecules
Human red blood cells
(red), activated platelets
(purple) and white blood
cells - monocyte (green)
and T lymphocyte
(orange).
Colorized-SEM
(scanning electron
micrograph)
Magnification:-1200x-(Based on an image
size of 1 inch in the
narrow dimension)
Part I Central Immune
organs
Central Immune Organs are the sites of
generation, differentiation and
maturation of immunocytes.
 Bone marrow
 Thymus
 Bursa of Fabricius
(the site of B cells
maturation in birds)
I. Thymus
The thymus is the site of T cell
differentiation and maturation.
1.The structure of Thymus
2. Cells in thymus and thymus
microenviroment
(1)Thymus stroma cells (TSC)
Thymus epithelial cells(TEC),
Fibrocyte,Macrophages, Dendritic
cells
(2)Thymocytes
The cells migrate from the bone
marrow to the thymus and then
become thymocytes
(3)Thymus microenviroment
 TSC
TEC: Secret thymus hormones and cytokines.
Interaction between cells by direct
contact.
 Extracellular matrix
 Active substance in local sites
3. Function of Thymus
(1) Development and differentiation of T
lymphocytes in thymus
 TSC interact with thymocytes directly by
adhesion molecules.
 TSC secrete various cytokines and thymus
hormones.
 Thymocytes secrete various cytokines.
(2)Immune regulation of the thymus
(3)Barrier function of the thymus
II. Bone marrow
The bone marrow is the site of generation of all
circulating blood cells in the adult, including
immature lymphocytes,and is the site of B cell
maturation.
Functions of bone marrow
 The site of generation of all immunocytes
 The site of differentiation and maturation of
immunocytes
 The site of immune response of B
cell,specifically in secondary immune response.
III.Bursa(Bursa of Fabricius)
 Specific immune organs in birds
 The site of differentiation and
proliferation of B cells in birds.
Part II Peripheral lymphoid organ
The site where lymphocytes locate,response to
foreign antigens ,produce specific antibody and
sensitized T lymphocytes.
 Lymph node
 Spleen
 Mucosal associated lymphoid tissue (MALT)
 Skin associated lymphoid tissue (SALT)
I. Lymph node ( LN)
Lymph nodes are the organs in which
adaptive immune responses to lymph-borne
antigens are initiated.
Here’s a chance to revise
your knowledge of:
A typical active lymphnode, e.g. in an
infection
From http://medicine.ucsd.edu/clinicalmed/head.htm
1
mm
Surface Locations of Lymph Node
Functions of lymph nodes
 Filter and eliminate foreign antigens.
 The site of immune response.
 The site of lymphocytes residence and
source of recirculation cells.
II. Spleen
The spleen is the major site
of immune responses to
blood-borne antigens.
Functions of spleen
 The site of immunocytes residence.
 The site of immune response.
 Produce some active substances,such as
complement,et al.
 Function of filtration.
III. SALT
The skin contains a specialized cutaneous
immune system consisting of lymphocytes
and APCs (such as Langerhan’s cell)
Cellular components of the cutaneous immune system
IV. MALT
The mucosal surfaces of the gastrointestinal
and respiratory tracts,like the skin,are
colonized by lymphocytes and APCs that
initiate immune responses to injested and
inhaled antigens.
Composition of MALT
(1) Gut-associated lymphoid tissue (GALT)

M cell: membranous epithelielial cell
---antigen transporting cell
(2)NALT(N:nasal)
(3)BALT(B:bronchial)
M cells establish
immunity in the
digestive tract
Functions of MALT and SALT
The first line of defense against foreign
antigen.
The site of immune response.
Participate in delayed hypresensitivity.
Part III Immunocytes
I. Hematopoietic stem cells and
differentiation
II. Immunocytes
1. Lymphocytes
2. Mononuclear phagocytes
3. Other cells
III Homing and recirculation of
lymphocytes
I. Homing of lymphocytes: the process by which
particular subsets of lymphocytes
selectively enter some tissues but not
others is called lymphocyte homing.
(homing receptor on T lymphocyte and ligand
on endothelial cell)
b
Lymphocytes
recirculation
and homing
 Naïve T lymphocytes home to lymph node
as a result of L-selectin binding to its
ligand on high endothelial venules,which are
present only in lymph nodes.
 Activated T lymphocytes,including
effective cells,home to sites of infection in
peripheral tissue,and this migration is
mediated by E- and P-selectins and
integrins.
2. Recirculation of lymphocytes
Lymphocyte recirculation is the process
lymphocytes circulate repeatedly among
blood,lymph,lymphoid organs and tissues.
3. Significance
 Promote lymphocytes to contact with antigen
throughout the body.
 Promote effector cells migrate to
inflammation sites rapidly.
 Promote lymph tissue acquire supplement of
new lymphocytes from circulatory pools.
 Memory cells can participate in recirculation
and secondary immune response.
Summary
Part IV Immune
molecules
Membrane molecules
Secretory molecules