第九章 免疫系统 by dffhrtcv3

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									Immune System
              Immune System
1 Constituents: Lymphocytes in blood vessels,
               lymphatic vessels and somewhere else,
               lymphatic tissues and lymphatic organs.

2 Function:    Destroy the invaders, such as
               pathogenic orgnisms and other
  antigens.
               Destroy the useless or harmful cells in
               human body, such as old RBC, cancer-
                         Lymphocyte
  Functionally, lymphocytes can be divided into 3 types:
  T cell, B cell and NK cell.

1.T-lymphocyte: educated in thymus and involved in cell-mediated
                  immune response.
Helper T-lymphocyte----(cluster of the differentiation)CD4+T-lymphocyte.
                       it can upregulate both cell-mediated immune
       HIV             response and humoral immune response;
Cytotoxic T-lymphocyte----CD8+T-lymphocyte. a kind of effector cells
                             cytotoxic/suppressor T- lymphocyte can
                            downregulate or turn off immune response
            2. B-lymphocyte

B-lymphocyte: educated in the bone marrow and
             involved in humoral immune response
       Ag


B-lymphocyte          plasma cell        antibody

       neutralize antigen
3. Natural killer lymphocyte


NK cell: effector cell.
         It can kill abnormal cells directly.
                Lymphatic tissue
1.defination: the tissue which is mainly composed of
                lymphocytes.
2. classification:(1) diffuse lymphatic tissue
                  (2) lymph nodule: lymph follicle
(1) diffuse lymphatic
          tissue

mainly composed of T lymphocytes
(2) lymph nodule
Also lymphoid follicle,mainly composed of B
lymphocytes.


After stimulation of antigen,the germinal center will
appear.


Classification:primary lymph nodule
                 secondary lymph nodule
lymphatic nodule: concentration of lymphocytes
                contained in the meshwork of reticular cells.
                mainly containing B cells together with some
                plasma cells, macrophages,etc..


primary nodule: without germinal center;


                       Ag
Secondary nodule: with germinal center (B cells
                   proliferates here rapidly).
        lymphatic organs

Primary (central) lymphatic organs
---- thymus and bone marrow
----site that T-lymphocytes and B-lymphocytes
    get educated respectively.

Secondary (peripheral) lymphatic organs
---- lymph node, spleen and tonsil
---- sites that immune responses are initiated.
                1. Thymus
Thymus: capsule ,thymic cortex and medulla
          Thymic cortex

Thymic cortex contains thymocytes (more )
and epithelioreticular cells (less).



Thymocytes: developing T-lymphocytes.about
            98% of them undergo
 apoptosis.
                 Thymic cortex

There are 3 types of epithelioreticular cells in the cortex.

Type I: Located at the boundary of the cortex and capsule.
          involved in the formation of blood-thymus barrier.

Type II: Located within the cortex .It is APC   and involved
            in thymic cell education
.
Type III: Located at the boundary of the cortex and medulla.
            A kinds of APCs to present Ag.
                 epithelioreticular cells

cortex
                  thymocytes
                 (85--90%)

medulla




          胸腺高倍
capsule




trabecula
epithelioreticular
cells
thymocyte
          Blood-thymus barrier
It is the structure between thymocytes and blood , a
physical barrier to protect developing T-lyphocytes
from exposure to Ag.
Components:     lining endotheium of capillary wall and
                its basal lamina;
                macrophages in the perivascular C.T.;
                type I endothelioreticular cells with
                their tight junctions.
Blood-thymus barrier
              Thymic medulla
It contains epithelioreticular cells (more) and
T lymphocytes(less).

T lymphocytes here are mature ones.


There have another 3 types of epithelioreticular cells

Type IV: located between the medulla and cortex;
Type V: located throughout the medulla;
Type VI: form the thymic or Hassall’s corpuscles in medulla
              Thymic corpuscle
Thymic corpuscle: a characteristic feature of the thymus.
                  It is a isolated mass of closely packed,
                  concentrically arranged type VI
                  epithelioreticular cells .
Found in the thymic medulla.
Function of the thymus


Site of T lymphocyte education
stem cells maturation and
differentiation into T lymphocytes
thymus
             2 .Lymph node
The structure of lymph node: capsule ,cortex and medulla
lymph node
                       Cortex
Cortex consists of superficial cortex, paracortex and sinuses

1. superfacial cortex is organized into nodules, mainly
                        composed of B-lymphocytes.
                It is also bone marrow-dependent cortex.

2. Paracortex is free of nodules, mainly composed of
              T-lymphocytes.
               It is also thymus-dependent cortex.

3.Sinuses is divided into subcapsular sinuses and trabecular
          sinuses where filter the flowing lymph through it.
Lymph node
Specialized high endothelial venules      (HEVs)


Location: in the paracortex

Function: entry of circulating lymphocytes into the
          lymph node---enlarging immune response
HEVs
   recirculation of of lymphocytes
                                           thymu
                      HEVs                    s



blood vessels                       lymph nodes




                lymphatic vessels
                                     Bone marrow
lymph node
                      Medulla
Medulla consists of medullary cords and sinuses.

Medullary cords: cords of lymphatic tissue containing
                 B cells,plasma cells and macrophages

Medullary sinuses: similar with the sinuses in the cortex
                    but with more macrophages.
Lymph node
Medullary cord and sinus
   Functions of lymph node

(1)filtering lymph;

(2)initiate immune responses.

     phagocytosis of macrophage;
     B cells proliferate and differentiate into
     plasma cells and memory B cells.
                     3. spleen
the structure of the spleen:capsule,red pulp and white pulp
           Capsule of the spleen

Capsule: C.T. containing myofibroblasts, blood vessels,etc.
                      Splenic sinus
         Red pulp
                      Splenic cord

                                     Cord of lymphatic tissue

spleen                                with lots of blood cells



                      Periarterial lymphatic sheath(PALS)
         White pulp
                                Paracortex in lymph node

                      Malpighian body(splenic nodule)


                          Lymphatic nodule in lymph node
capsule
White pulp

trabecula




Red pulp
spleen
          White pulp

Malpighian body:

Periarterial lymphatic sheath:
A thick accumulation of lymphocytes
surrounding the artery.
White pulp
                  White pulp


Malpighian body




PALS
                   Red pulp

It contains large number of blood cells that it filters
and degrades.
Splenic cord: a meshwork of reticular cells and fibers
              containing lots of RBCs, macrophages,
              plasma cells,etc.


Splenic sinus: special sinusoidal vessels lined by rod-
               shaped epithelial cells. The processes
              of macrophages extend into the sinuses.
                red pulp



Splenic cord



Splenic sinus
脾
窦
扫
描
电
镜




Splenetic sinusoid
          Function of the spleen
It performs both immune and hemopoietic functions

1. filtering blood: killing pathogenic Ag and destroying
  senescent, abnormal RBC ,etc.;
   Splenectomy----increasing abnormal RBC in blood
   Splenomegaly----malaria

2. initiation of immune responses;

3. formation of blood cells during early fetal life;

4. storage of blood.
spleen
                        Key points
1.T-lymphocytes get mature in thymus while B-lymphocytes get mature
   in the bone marrow.B-lymphocytes can convert to plasma cells
   which are responsible for producing Ab.


2. The structure and function of thymus: cortex and medulla . Hassall’s
   corpuscle and blood-thymus barrier.

3.The structure and function of lymph node;the celular components of
   lymphatic nodule and paracortex.

4.The structure and function of spleen:red pulp and white pulp
   ( malpighian body and ).
                         Thymic cortex
 There are 3 types of epithelioreticular cells in thymic cortex.


                   epithelioreticular cells

        Type I                        Type II                       Type III

Located at the boundary of the
                                                         Located at the boundary of the
cortex and capsule.
                                                         cortex and medulla.
Serve as a barrier that isolate
                                                         A kinds of APCs to present Ag.
thymocytes and C.T.

                     Located within the cortex .
                     It is APC with MHC II molecules
                     which are involved in thymic cell
                     education.
     antigen-presenting cell (APC)

1. function:sequestering Ag and presenting
              it to helper CD4+T lymphocyte to
              facilitate immune responses.

2. components:macrophages,Kuffer cells of liver,
              Langerhans’ cells in epidermis,
              reticular dentritic cells of spleen
              and lymph node,
              type II and type III epithelioreticular
              cell of the thymus and B lymphocyte
Process of antigen-presenting
MHC (major histocompatability gene complex)


MHC I: expressed on the surface of all
       nucleated cells and platelets.

MHC II: expressed on the surface of all APCs.
    Circulation in the spleen
Branches of splenic artery enter the white pulp
from trabeculae;

Central artery :sends branches to white pulp
              itself and marginal sinuses;
              continues to penicillar
              arterioles in splenic cord ;

Penicillar arterioles continue with sheathed
capillaries which are empty the blood in the
cord,then the blood cells enter the splenic sinuses.

								
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