Primary Organs of the Immune System

8/12/2019 Primary Organs of the Immune System

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Thymus

The thymusis a speciali2zed organ of theimmune system.Within the thymus,T-cells,critical to theadaptive immune

system,mature

Located above the heart, below the thyroid and behind the

upper part of the sternum

a) cortex ( general word meaning outer layer) - Immature

T cells (thymocytes) start here.

b) medulla(general word meaning interior)Final

Quality check.

Site of T-cell maturation (details of the process later)

a. Cells rearrange genes for TCR (the T-cell receptor) in cortex.b. Cells are checked for the ability to recognize antigen on MHC with

the correct affinity (positive selection) in cortex.

c. Cells that survive selection travel through the medulla and undergo

selection to remove self-reactive cells (negative selection).

d. Cells that survive enter the circulation.

e. Cells that do not (over 95%) undergo apoptosis.

The thymus is made up of two lobes that join in front

of the trachea. Each lobe is made of lymphoid

tissue, consisting of tightly packed white blood cellsand fat.

Its function is to transform lymphocytes (white blood

cells developed in the bone marrow) into T-cells

(cells developed in the thymus). These cells are then

transported to various lymph glands, where they play

an important part in fighting infections and disease.

Swelling of lymph glands and fever are a signal that

immune cells are multiplying to fight off invaders of the body: bacteria, fungi,

viruses or parasites.

In addition to immune function, the thymus also produces hormones that promote

growth and maturation.

http://www.healthline.com/human-body-maps/thymus#4/1

2Concretamente, la funcin del timoes la de madurar y diferenciar los linfocitos T provenientes de la mdula

sea(estas clulas son un tipo deleucocitooglbulo blanco, cuya cometido general esreconocer y destruir

sustancias extraas o agentes infecciosos). Desde la corteza hasta la mdula existe un gradiente dediferenciacin, de modo que en la corteza se encuentran los timocitos ms inmaduros, mientras que en lamdula se localizan los timocitos en fases madurativas ms avanzadas.
http://en.wikipedia.org/wiki/Immune_systemhttp://en.wikipedia.org/wiki/Immune_systemhttp://en.wikipedia.org/wiki/T-cellhttp://en.wikipedia.org/wiki/T-cellhttp://en.wikipedia.org/wiki/T-cellhttp://en.wikipedia.org/wiki/Adaptive_immune_systemhttp://en.wikipedia.org/wiki/Adaptive_immune_systemhttp://en.wikipedia.org/wiki/Adaptive_immune_systemhttp://en.wikipedia.org/wiki/Adaptive_immune_systemhttp://www.healthline.com/human-body-maps/thymus#4/1http://www.healthline.com/human-body-maps/thymus#4/1http://www.healthline.com/human-body-maps/thymus#4/1http://en.wikipedia.org/wiki/Adaptive_immune_systemhttp://en.wikipedia.org/wiki/Adaptive_immune_systemhttp://en.wikipedia.org/wiki/T-cellhttp://en.wikipedia.org/wiki/Immune_system


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Secondary Organs of the Immune System

An interconnected surveillance system3, where the immune cells gather and

exchange information

Circulation among the organs: lymph makes a one-way trip, while blood makes a

round trip.

Blood moves immune cells throughout the body (along with

erythrocytes)

The lining of vessels (endothelium) responds to infections with

inflammation and this directs neutrophils and other immune

cells to the infected site.

Proteins in blood plasma include antibodies, clotting proteins

and complement proteins that attack foreign cells.

Blood filtered by spleen, which recycles aged erythrocyte and

picks of antigen and other detritus.

The lymph system is a network of organs, lymph nodes,lymph ducts, and lymph vessels that make and movelymph4from tissues to the bloodstream. The lymphsystem is a major part of the body's immune system.

Lymphis the fluid that circulates throughoutthelymphatic system.The lymph is formed when

theinterstitial fluid is collected throughlymph

capillaries.Lymph is a clear-to-white fluid made of:

White blood cells, especially lymphocytes, the

cells that attack bacteria in the blood

Fluid from the intestines called chyle, which

contains proteins and fats

3rganos linfoides primarios o centrales, que proporcionan el entorno para la maduracin de linfocitos (linfopoyesis), de

modo que los linfocitos adquieren su repertorio de receptores especficos para cada tipo de antgeno; los linfocitos seseleccionan de modo que poseen autotolerancia (evitacin de la autoinmunidad).

rganos linfoides secundarios o perifricos, que proporcionan el entorno para que los linfocitos interaccionen entre s, ocon las APC y otras clulas accesorias, y para que entren en contacto con el antgeno;diseminan la respuesta inmune alresto del cuerpo.

4 La linfa es un lquido incoloro compuesto de glbulos blancos, protenas, grasas y sales. Se transporta desde los tejidoshasta la sangre a travs de los vasos linfticos.En el sistema linftico no existe una bomba que impulse la linfa, a diferencia de lo que ocurre en el aparato circulatorio sinoque se mueve, aprovechando las contracciones musculares. El sistema linftico es laestructura anatmica que transportalalinfa unidireccionalmente hacia elcorazn,y es parte delaparato circulatorio.
http://en.wikipedia.org/wiki/Lymphatic_systemhttp://en.wikipedia.org/wiki/Interstitial_fluidhttp://en.wikipedia.org/wiki/Lymph_capillaryhttp://en.wikipedia.org/wiki/Lymph_capillaryhttp://es.wikipedia.org/wiki/Sistema_biol%C3%B3gicohttp://es.wikipedia.org/wiki/Linfahttp://es.wikipedia.org/wiki/Coraz%C3%B3nhttp://es.wikipedia.org/wiki/Aparato_circulatoriohttp://es.wikipedia.org/wiki/Aparato_circulatoriohttp://es.wikipedia.org/wiki/Coraz%C3%B3nhttp://es.wikipedia.org/wiki/Linfahttp://es.wikipedia.org/wiki/Sistema_biol%C3%B3gicohttp://en.wikipedia.org/wiki/Lymph_capillaryhttp://en.wikipedia.org/wiki/Lymph_capillaryhttp://en.wikipedia.org/wiki/Interstitial_fluidhttp://en.wikipedia.org/wiki/Lymphatic_system


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Lymph also provides transport of immune cells,

primarily lymphocytes, but no erythrocytes

Drains interstitial fluid from tissues, picking up

antigens and white cells Lymph (fluid) filtered through lymph nodes, where

antigen is trapped and acted on.

Vessels join into larger ones that empty into the

thoracic duct, which in turn empties into left subclavian

vein and then enters heart.

Lymph nodes5: Trap antigen and provides sites for thelymphocytes to interact with antigen. The lymph nodes act as

filters along the lymphatic system. These nodes trap germs

like bacteria,viruses,toxins as well ascancer cells and

ensure that these are removed from the body.

Basic structure

a) cortex receives incoming lymph (afferent)

b) follicles embedded in cortex receive and hold B cells

c) paracortex (immediately inside) hold T cells

d) mature B cells leave through this

e) exit out the efferent vessels

Cell interactions

B cells activated by antigen migrate

to the paracortex to alert T cells. Some

get instruction to go forth and make

antibodies.

Secondary follicle develops after antigen exposure. Has active

germinal center where B cells develop in response to signal from

follicular dendritic cells, TH cells and macrophages. B cells that have spent time in a secondary follicle learn to

make more effective antibodies. Undergo affinity maturation

5Los ndulos linfticos son acumulos delinfocitosbien definidos contenidos en una malla de fibras reticulares, que no

presentancpsula.El sistema linftico es una compleja red de vasos angostos, vlvulas, conductos, ndulos y rganos. Ayuda a proteger y amantener el ambiente de fluidos del organismo produciendo, filtrando y transportando linfa, y produciendo diversos glbulos.Los ndulos linfticos cumplen una importante funcin en la defensa del cuerpo contra las infecciones.Los vasos linfticos aferentes llevan fluidos no filtrados al ndulo linftico para que sean filtrados, mientras que los vasoseferentes sacan fluidos limpios del ndulo linftico y al sistema cardiovascular, en donde ayudan a formar el plasma de lasangre. Cuando el cuerpo resulta invadido por organismos forneos, la dolorosa inflamacin que se siente a veces en el cuello,las axilas, la ingle o las amgdalas es causada cuando los microorganismos resultan atrapados dentro de colecciones de clulaso ndulos linfticos. Al final, estos organismos son destruidos y eliminados por clulas que recubren las paredes de los nduloslinfticos y el dolor y la inflamacin disminuyen.
http://www.news-medical.net/health/What-is-a-Virus.aspxhttp://www.news-medical.net/health/What-is-Cancer.aspxhttp://es.wikipedia.org/wiki/Linfocitohttp://es.wikipedia.org/wiki/Linfocitohttp://es.wikipedia.org/wiki/Linfocitohttp://es.wikipedia.org/wiki/C%C3%A1psula_(fruto)http://es.wikipedia.org/wiki/C%C3%A1psula_(fruto)http://es.wikipedia.org/wiki/C%C3%A1psula_(fruto)http://es.wikipedia.org/wiki/C%C3%A1psula_(fruto)http://es.wikipedia.org/wiki/Linfocitohttp://www.news-medical.net/health/What-is-Cancer.aspxhttp://www.news-medical.net/health/What-is-a-Virus.aspx


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Spleen:

The spleen6plays multiple supporting roles in

the body. It acts as a filter for blood as part of

the immune system. Old red blood cells are

recycled in the spleen, and platelets and whiteblood cells are stored there. The spleen also

helps fight certain kinds of bacteria that cause

pneumonia and meningitis.

I. in abdomen, next to pancreas

II. filters blood, not lymph

III. red pulp with macrophages that recycle old red blood cells

IV. white pulp (PALS) has T cells

V. marginal zone with B cells in follicles - system works like the lymph

nodes:

VI. Removing the spleen can increase a person's risk for bacterial

infections, but there does seem to be some redundancy in the system

as a whole.

6Bazo, Su funcin principal es la destruccin declulas sanguneas rojasviejas, producir algunas

nuevas y mantener una reserva desangre.La pulpa roja se compone de clulas sanguneas tales como plaquetas, granulocitos, y los corpsculos rojos de

la sangre. Acta como un filtro y limpia la sangre mediante la eliminacin de los antgenos y los glbulos

rojos daados.

La pulpa blanca acta como una fuente de anticuerpos y linfocitos para el sistema inmunolgico de defensa.

Area Function Composition

red pulp

Mechanical filtration

ofred blood cells.In

mice: Reserve

ofmonocytes[4]

"sinuses"(or "sinusoids"), which are filled with

blood

"splenic cords"ofreticular fibers

"marginal zone"bordering on white pulp

white pulp

Active immune

response through

humoral and cell-

mediated pathways.

Composed of nodules, calledMalpighian corpuscles.

These are composed of:

"lymphoid follicles"(or "follicles"), rich inB-lymphocytes

"periarteriolar lymphoid sheaths"(PALS), rich inT-

lymphocytes
http://es.wikipedia.org/wiki/Eritrocitohttp://es.wikipedia.org/wiki/Eritrocitohttp://es.wikipedia.org/wiki/Sangrehttp://es.wikipedia.org/wiki/Sangrehttp://es.wikipedia.org/wiki/Sangrehttp://en.wikipedia.org/wiki/Red_pulphttp://en.wikipedia.org/wiki/Red_pulphttp://en.wikipedia.org/wiki/Red_blood_cellshttp://en.wikipedia.org/wiki/Monocytehttp://en.wikipedia.org/wiki/Monocytehttp://en.wikipedia.org/wiki/Monocytehttp://en.wikipedia.org/wiki/Sinus_(anatomy)http://en.wikipedia.org/wiki/Sinusoid_(blood_vessel)http://en.wikipedia.org/wiki/Splenic_cordshttp://en.wikipedia.org/wiki/Reticular_fiberhttp://en.wikipedia.org/wiki/Marginal_zonehttp://en.wikipedia.org/wiki/White_pulphttp://en.wikipedia.org/wiki/White_pulphttp://en.wikipedia.org/wiki/White_pulphttp://en.wikipedia.org/wiki/Lymphoid_follicleshttp://en.wikipedia.org/wiki/B_cellhttp://en.wikipedia.org/wiki/Periarteriolar_lymphoid_sheathshttp://en.wikipedia.org/wiki/T_cellhttp://en.wikipedia.org/wiki/T_cellhttp://en.wikipedia.org/wiki/T_cellhttp://en.wikipedia.org/wiki/T_cellhttp://en.wikipedia.org/wiki/Periarteriolar_lymphoid_sheathshttp://en.wikipedia.org/wiki/B_cellhttp://en.wikipedia.org/wiki/Lymphoid_follicleshttp://en.wikipedia.org/wiki/White_pulphttp://en.wikipedia.org/wiki/White_pulphttp://en.wikipedia.org/wiki/Marginal_zonehttp://en.wikipedia.org/wiki/Reticular_fiberhttp://en.wikipedia.org/wiki/Splenic_cordshttp://en.wikipedia.org/wiki/Sinusoid_(blood_vessel)http://en.wikipedia.org/wiki/Sinus_(anatomy)http://en.wikipedia.org/wiki/Monocytehttp://en.wikipedia.org/wiki/Monocytehttp://en.wikipedia.org/wiki/Red_blood_cellshttp://en.wikipedia.org/wiki/Red_pulphttp://es.wikipedia.org/wiki/Sangrehttp://es.wikipedia.org/wiki/Eritrocito


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Mucosal-Associated Lymphoid TissueMALT7

Also gut associatedGALT, andbronchial (lung epithelia)BALT, nasalNALT, CALT (conjunctival-associated

lymphoid tissue)

Constitutes the most extensive component

of human lymphoid tissue, these surfaces

protect the body from an enormous

quantity and variety of antigens.

The mucosa of the digestive, respiratory,

and urogenital systems represents the

major site of entry of most pathogens. The epithelia of these systems contain

defensive lymphoid tissues.

Organized structures present include tonsils, appendix, and Peyr's patches8in the

intestine

Tonsils9are collections of lymphoid tissuefacing into the aerodigestive tract.Theseimmunocompetenttissues are theimmune system's first line of defense against ingested or

inhaled foreignpathogens.

Peyer's patches (or Peyer patches) are round or ovoid bundles of lymphatic tissue

made up of unencapsulated lymphatic cells that protect the mucous membranes of

the small intestines (the ileum) from infection.

Epithelial cells of the mucosa deliver antigen samples from the lumen10

(spaces

inside of tubular-shaped structures within the body.), delivering them via M cells

M cells are large epithelial cells, each with a number of smaller immune cells

residing in the basolateral pocket it makes.

Antigen crosses the plasma membrane to these. The B cell then migrates to

inductive sites.

7tejido linfoide asociado a las mucosas: es un tipo de agrupacin de clulas linfoides sin

organizacin o estructura,Tejido linfoide asociado a los bronquios o BALT,se encuentra en lamucosa que recubre las vas respiratorias. Contienelinfocitos ByT.Tejido linfoide asociado al tubodigestivo o GALT, Se compone de folculos linfoides a todo lo largo del tubo gastrointestinal casitodos estn aislados entre si.Tejido linfoide asociado a la nariz o NALT (nose-associated lymphoid tissue).Tejido linfoide asociado a la conjuntiva o CALT (conjunctiva-associated lymphoide tissue)

8placas de Peyerson unos cmulos detejido linftico(ndulo linftico)que recubren interiormente

lasmucosascomo las del intestino.9Las amgdalasson extensiones de tejido linfoide situados en la faringey que constituyen elanillo

de Waldeyer,protegiendo la entrada de las vas respiratorias de la invasin bacteriana. 10es el espacio interior de una estructura tubular, como en una arteriaointestino
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Skin

The largest organ of the body, not technically a

Secondary Lymphoid Organ ( we can consider it as a

tertiary organ)

1. Important in innate defenses

Keratinocyte11is the predominantcell type intheepidermis,the outermost layer of theskin,

constituting 90% of thecells found there. The primary

function of keratinocytes is the formation of a barrier

against environmental damage such aspathogens,heat,UV radiation andwater

loss.Epithelial cells (keratinocytes) of the outer layer secrete cytokines. Also die,

leaving behind keratin intermediate filament as a protective barrier

2. Important in adaptive defenses

a. Keratinocytescan express class II MHC and present antigen.

b .Langerhans cellsaredendritic cells(antigen-presenting immune cells) oftheskinandmucosa.They are present in all layers of the epidermis, but are most

prominent in thestratum spinosum.

Langerhans (dendritic) cell phagocytize antigen and carry it to lymph

nodes.

Also carry class II MHC and activate TH cells.

c. Intraepidermal (a form of intraepithelial) lymphocyte, or IELs, manywith specialized T cell receptors) - activated or memory cells

11queratinocitos, Los queratinocitos son las clulas que producen queratina y adems producen

citocinas que son molculas solubles con funciones de regulacin de las clulas epiteliales yclulas drmicas
http://en.wikipedia.org/wiki/Cell_(biology)http://en.wikipedia.org/wiki/Epidermis_(skin)http://en.wikipedia.org/wiki/Skinhttp://en.wikipedia.org/wiki/Cell_(biology)http://en.wikipedia.org/wiki/Pathogenshttp://en.wikipedia.org/wiki/Heathttp://en.wikipedia.org/wiki/UV_radiationhttp://en.wikipedia.org/wiki/Dehydrationhttp://en.wikipedia.org/wiki/Dehydrationhttp://en.wikipedia.org/wiki/Dendritic_cellshttp://en.wikipedia.org/wiki/Dendritic_cellshttp://en.wikipedia.org/wiki/Dendritic_cellshttp://en.wikipedia.org/wiki/Skinhttp://en.wikipedia.org/wiki/Skinhttp://en.wikipedia.org/wiki/Skinhttp://en.wikipedia.org/wiki/Mucosahttp://en.wikipedia.org/wiki/Mucosahttp://en.wikipedia.org/wiki/Mucosahttp://en.wikipedia.org/wiki/Stratum_spinosumhttp://en.wikipedia.org/wiki/Stratum_spinosumhttp://en.wikipedia.org/wiki/Stratum_spinosumhttp://en.wikipedia.org/wiki/Stratum_spinosumhttp://en.wikipedia.org/wiki/Mucosahttp://en.wikipedia.org/wiki/Skinhttp://en.wikipedia.org/wiki/Dendritic_cellshttp://en.wikipedia.org/wiki/Dehydrationhttp://en.wikipedia.org/wiki/Dehydrationhttp://en.wikipedia.org/wiki/UV_radiationhttp://en.wikipedia.org/wiki/Heathttp://en.wikipedia.org/wiki/Pathogenshttp://en.wikipedia.org/wiki/Cell_(biology)http://en.wikipedia.org/wiki/Skinhttp://en.wikipedia.org/wiki/Epidermis_(skin)http://en.wikipedia.org/wiki/Cell_(biology)


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A. Apoptosis

One aspect of the immune system that makes it so energetically expensive isthat it produces huge numbers of cells and then gets rid of the great majorityof cells before they are even used.

1. Analogous to imploding a building.

a. Cell shrinks

b. Chromatin condenses

c. Membrane blebs

d. Cell fragments into intact pieces, easily phagocytized

2. Necrosisanalogous to blowing up a building (figure)

a. Organelles swell and break down

b. Cell disintegrates

c. Contents released where they can cause tissue damage and inflammation

d. Much harder to clean up after

Evolution

Ancestral chordates, which gave rise to the vertebrate members of thephylum

Chordata, do not have an adaptive immune system.


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1. The first fish to evolve were jawless and we have only a few remainingexamples

of this type, among them the lamprey eel. These eels have B cells, GALT and

some thymic tissue with T cells at the tips of their gills.

2. Other fish have immune tissue around the gut, as well as spleens anddefined

thymic tissue. (figure)

3. Amphibians, reptiles, birds and mammals all have bone marrow, but theirB cells

mature in a variety of places.

Immunology L2, Survey of Cells and Organs- 5

4. So, while its true that reptiles, bird and mammals have B cells and T cell

along

with their innate defenses, there is a lot of variety in what gets made whereand

when.

5. Happily rodents and humans have reasonably similar immune systems,making

mice and rats good lab models for the study of the immune response.


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Complejo mayor de histocompatibilidadPresenta antigenos a los linfositos, permiten que el sistema inmunereconosca sus celular como propias y no como antgenos

Clase I,en la membrana de todas las clulas, prsentan antgeno a linfocitoscd8, citotoxicos


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Clase II, solo en clulas inmune, presentan antgeno a los linfositos tcolaboradsores

Elepitelioes eltejidoformado por una o varias capas declulasunidas entre s, que puestasrecubren todas las superficies libres del organismo, y constituyen el revestimiento interno de las

cavidades, rganos huecos, conductos del cuerpo, as como forman lasmucosasy lasglndulas.
http://es.wikipedia.org/wiki/Tejido_(biolog%C3%ADa)http://es.wikipedia.org/wiki/Tejido_(biolog%C3%ADa)http://es.wikipedia.org/wiki/Tejido_(biolog%C3%ADa)http://es.wikipedia.org/wiki/C%C3%A9lulahttp://es.wikipedia.org/wiki/Mucosahttp://es.wikipedia.org/wiki/Mucosahttp://es.wikipedia.org/wiki/Mucosahttp://es.wikipedia.org/wiki/Gl%C3%A1ndulahttp://es.wikipedia.org/wiki/Gl%C3%A1ndulahttp://es.wikipedia.org/wiki/Gl%C3%A1ndulahttp://es.wikipedia.org/wiki/Gl%C3%A1ndulahttp://es.wikipedia.org/wiki/Mucosahttp://es.wikipedia.org/wiki/C%C3%A9lulahttp://es.wikipedia.org/wiki/Tejido_(biolog%C3%ADa)

Primary Organs of the Immune System

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