immune system blok5

7/25/2019 Immune System Blok5

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Department of Histology FK UNSRI

Lymphoid and Immune

Systems


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In this chapter, the following are

examined:

1.Overview of Immune System

2.General organisation of alymphatic organ.

.Structure and function of the

thymus, lymph nodes and spleen.


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The Immune ResponseImmunity: Free from burden. Ability of an

organism to recognize and defend itselfagainst specifcpathogens or antigens.

Immune Response: Third line of defense.

Involves production of antibodies andgeneration of specialized lymphocytesagainst specic antigens.

Antigen: !olecules from a pathogen orforeign organism that provo"e a specicimmune response.


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The Immune #ystem is the

Third $ine of %efenseAgainst Infection


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&omponents of 'umanImmune #ystem


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Immune System

contents:1. Immune !ells

2. "ymphoid #issues. "ymphoid Organs


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(. Immune &ells:(.( $ymphocytes.(.) &ells of mononuclearphagocyte system.(.* Antigen+ presenting cells,A-&


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). $ymphoid tissues:

).( di/use lymphoid tissue ).) lymphoid nodule

*. $ymphoid organs *.( central lymphoid organs

,thymus0 bone marro1

*.) peripheral lymphoidorgans ,lymph nodes0 spleenand tonsils


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Functions:

a. immunologic defense: recogni$ingand removing antigens that invade intothe %ody.%. Immunologic surveillance:removing %ody cells with changedsurface antigens.

c. Immunologic homeostasis:removing aging, dead and damaged

cells.


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1. Immune cells

(.( $ymphocytes !lassi&ed into classes:# !ells, '

!ells and () !ells

a. T cells* Stem cells migrate from the %onemarrow through the %lood andinvade thethymus.


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* (aive # cells enter peripherallymphoid organs, under stimulationof speci&c antigens, proliferate

and transform into e+ector # cellsandmemory # cells.

* esponsi%le for cellular immunity-directly ill target cells/.


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* # cells are divided into

su%populations: a. helper T cell ( Th ),

b. cytotoxic T cell ( Tc ),

c. suppressor T cell ( Ts ).


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b.2 cells* Stem cells undergo a series of

changes in the%one marrowto form' cell.* (aive ' cells enter peripheral

lymphoid organs or lymphoid tissues,under stimulation of speci&c antigens,proliferate and transform into plasma

cells - e+ector ' cell/ and memory 'cells.* esponsi%le for humoral immunity.


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c. 34 cells

-"ac marers characteristic of #and ' cells.

-0ccount for 1 3 14 of totallymphocytes in the peripheral%lood.

* 0ttac virus*infected cells andcancer cells without previousstimulation.


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(.)!acrophages and

mononuclear phagocytesystem , !-# 0 group of cells that are widely

distri%uted collection ofphagocytes. #hey are derivedfrom monocytes.


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!-# includes

5onocytesin the %lood and %onemarrow.5acrophagesin connective tissue,

lymphoid tissue, peritoneal andpleural cavities and lungs -dustcells/.

)up+ercells in the liver6

Osteoclastsin the %one65icroglial cells of the nerve tissue6"angerhanscells in the sin.


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(.* Antigen

presenting cells ,A-&7ave the ma8or histo*

compati%ility complex

molecules -57!/.7ave the capacity to capture

and process antigens, form apeptide* complex and thenpresent the complex to # cells.

5ainly include dendritic cells-9!s/and macrophages.


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2. Lymphoid tissue

reticular tissue lymphocytes

a. %i/use lymphoid tissue 3 looselypaced lymphocytes within !#

b. $ymphoid nodules3 denselypaced lymphocytes within loose

!#* tonsils

* aggregated lymphoid nodules--eyer5s patches/


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).( %i/use lymphoid

tissue

Diffuse collection of lymphocytes !"or # cells$% no clear &oundary.

Lymphoid nodules appear after

antigen stimulation.


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'ontains postcapillary% or high endothelial

(enule% as passages of lymphocytes to enter

the &lood.


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).) Lymphoid nodules

!Lymphoid follicles$Spherical

collections ofdenselypac)ed

lymphocytes

!mainly # cells$.


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Copyright 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

$ymphoid Tissue 'istology


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Copyright 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Tonsils


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*fter antigen

stimulation% the

primary nodule&ecomes larger +ith

germinal center% called

the secondary nodule.

"he ,erminal center

di(ides into dar) -one

and light -one% the

latter is co(ered &y a

cap.


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3. Lymphoid organs 3.1 central lymphoid organs

(thymus, bone marrow)

3.2 peripheral lymphoidorgans (lymph nodes, spleenand tonsils)


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*.( Thymus

edulla

'orte/

'apsule

a central lymphoid organ,eneral description


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a. &apsule

connecti(e tissueinterlo&ular septa

"hymic lo&ules.0ach lo&ule has aperipheral dar)

-one!corte/$and acentral light-one!medulla$.


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b. &orte7

"hymic epithlial

cells or epithelial

reticular cells forma mesh+or).

Numerous% densely

pac)edlymphocytes%

termed thymocytes


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"hymic epithelial cells

"hese cells are

large and&ranched% and

desmosomes

&et+een ad1acentcells.


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"hymocytes

"hese are densely pac)edand do not form nodules.

"hey arise &y di(ision of

stem cells +hich comefrom the &one marro+.

ost degenerate and areremo(ed &ymacrophages% only asmall num&er +ill matureand lea(e the thymus.

! d ll


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c. !edulla

Rich in epithelial cells%fe+er lymphocytes.

Hassallsor thymic

corpuscles

"hese composed of

concentrically

arranged epithelialreticular cells that

degenerate.

2l d th b i


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2lood+thymus barrier

* continuous capillaryendothelial layer.

"he &asal lamina of theendothelial cells.

* pericapillary spacecontainingmacrophages.

* continuous layer andthe &asal lamina of theepithelial reticular cells.


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Functions

icroen(ironment for &one

marro+3 deri(ed lymphocytes

!stem cell$ to proliferate into "

cells.

Secretion !&y the epithelialreticular cells$ of thymosin and

thymopoietin.


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*.) $ymph nodes

peripherallymphoid organs%lying along the

course oflymphatic (essels

'apsule

'orte/edulla

'apsule

'orte/

edulla


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a. 'apsule

'onnecti(e tissue se(eral afferent

lymphatic (essels .

"ra&eculae e/tendfrom the capsule intothe parenchyma.

4ne or t+o efferentlymphatic (esselslea(e at thehilum


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b. &orte7

#eneath the capsule%three structuralcomponents

Superfacial corte/

'ortical lymphoid

sinuses


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b.( #uperfacial corte7

'ontains lymphoidnodulesand diffuselymphoid tissue in&et+een.

It is mainly populated&y # cells.

5hen stimulated &yantigen% a lymphoid

nodule responds &yforming a germinalcenter.


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b.) -aracortical zone

Diffuse lymphoid

tissue +ith " cells

! thymus dependentarea.

Numerous

postcapillary (enules


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b.* &ortical lymphoid

sinusesIncludesu&capsular sinusand

peritra&ecularsinuses .

'ontain reticular

cells and fi&ers%macrophages andlymphocytes.


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c. !edulla8 )

componentsedullary cordsare lymphoid tissue

cords +ith many #

cells and plasma

cells.

edullary

lymphoid sinuses

are similar to the

cortical sinuses.


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Functions

Ser(e as a filter for lymph33lymph percolate slo+ly.

Sites for immune responses6under stimulation of antigens%&oth # and " cells proliferate

and produce anti&odies andeffector " cells causing humoraland cellular immunity.

l h l ti


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lymph percolating


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Recirculation of

lymphocytesDefinition7 Lymphocytes circulate

repeatedly from lymphoid tissueandorgans through the lymphatic (esselsand into the &loodstream. "he mostacti(ely recirculating cells are

memory cellsof &oth " and # cells.


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'ourse7 Lymphocytes in the

&lood stream cross the +all ofpostcapillary (enulesinto the

lymphoid tissue.

Lymphocytes in the lymphoid

tissue enter lymphatic (essels%

then into the &loodstream.

Recirculation of lymphocytes


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Recirculation of lymphocytes

lymphoid tissue /organs

postcapillary lymphatic enules essels

bloodstream


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Significance7 to increase the pro&a&ility

of meeting antigens% distri&ute

information concerning antigens% and

unite the different parts of the immune

system.


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*.*. #pleen* thic)capsuleof dense connecti(e

tissue% co(ered &y mesothelium andcontaining smooth muscle cells."ra&eculaee/tend from capsule into theparenchyma.

"he parenchyma is made up of the +hitepulpand red pulp.


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capsule

trabecula

White pulp

red pulp

!pleen


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a.9hite pulp

8eriarterial

lymphatic sheath

Lymphoid

nodules


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!9$8eriarterial lymphatic sheath

Diffuse lymphoid tissue sheath encircling acentral artery.

ainly contains " cells !thymus3dependent

area$% some macrophages.!2$Lymphoid nodules

*ppended to the sheath and rich in # cells.

Ha(e germinal centers +hen stimulated &y

antigens.


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!:$ arginal -one

Lies &et+een the +hite and red pulps%consisting of many marginal sinuses"he marginal -one har&ours an

a&undance of &lood antigens and thusplays a ma1or rolein the immunologicacti(ity of the spleen.

Lymphocytes in the +hite pulp enter the

marginal sinuses to ta)e part inrecirculation.


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"arginalsinuses

"arginal#one

$hite pulp

Red pulp


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b. Red

pulp#plenic

&ords

!plenic!inus

!9$ S l i d


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!9$ Splenic cords

a.Diffuse lymphoid tissue organi-ed in

cords% containing # cells% plasma cells.&.ost capillaries open and pour &lood

into the cords% so rich in erythrocytes.

!2$ Splenic sinusoids


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!2$ Splenic sinusoids

a. Lined &y elongated endothelial cells+ith

+ide spaces &et+een them.

&. Fle/i&le &lood cells pass from splenic

cords to the lumen of the sinus.


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Functions

#lood filter! remo"al o# agederythrocytes and platelets in splenic

cords.

Immune responses! similar to lymph

nodes.

8roduction of lymphocytes.#lood storage.


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Than"s for your"indly patient andattention

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