aspectos basicos inmun peru 2013
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ASPECTOS BASICOS DELSISTEMA INMUNE
Dr Heraldo Povea PacciMD (Chile) MSc (Gran Bretaa) Fellow (EEUU) PhD (Australia)
Miembro Comit Inmunizaciones Ministerio Salud Chile
Profesor Asociado . Universidad Diego Portales Chile
Especialista en Inmunologia y Salud Sexual
Consultor en Educacion Superior
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Plan de la presentacion
Nomenclatura
Componentes del sistema de defensas Las respuestas defensivas
Control del sistema
Alteraciones del sistema
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Definitions
Immune system = cells, tissues, and moleculesthat mediate resistance to infections
Immunology = study of structure and function of
the immune system
Immunity = resistance of a host to pathogens and
their toxic effects
Immune response = collective and coordinated
response to the introduction of foreignsubstances in an individual mediated by the cells
and molecules of the immune system
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Role of the immunesystem Defense against microbes
Defense against the growth of tumor cells
kills the growth of tumor cells
Homeostasis
destruction of abnormal or dead cells
(e.g. dead red or white blood cells, antigen-
antibody complex)
Other unknown functions?
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ORGANOS CENTRALES
Mdula sea
Timo
ORGANOS PERIFRICOS
Adenoides
Amgdalas
Ganglios linfticos
Bazo
Apndice
Placas de Peyer
BALT (Tejido linftico asociado abronquios)
GALT (Tejido linftico asociado a intestino)
SALT (Tejido linftico asociado a la piel)
ORGANOS DEL SISTEMA INMUNE
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Clula tronco pluripotencial de la mdula sea
Progenitor linfoideProgenitor B Clula NK Progenitor T
Clula pre-B Pre-Timocito
Clula B inmadura Timocito inmaduro
Clula B madura Timocito maduroLinfocito B Linfocito T
Clula Plasmtica Linfocitos Th y Tc
Inmunoglobulinas Linfoquinas
IgM Th1 Th2
IgG IL-2 IL-3 IL-4
IgA INF-g GM-CSF IL-13
IgE TGF-b IL-5
IgD IL-9
FUNCIONES
Respuestainmune humoral
Memoria
Respuestainmune celular
Hipersensibilidad
retardada
Citotoxicidad
Memoria
prolongadaInmunidad
anti-tumoral y
anti-viral
Citotoxicidad NK
CLULAS DEL SISTEMA INMUNE
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LINFOCITOS T
Representan el 60-70% de los linfocitosperifricos.
Ubicados en regiones paracorticalesde ganglios linfticos y manguitosperiarteriolares del bazo.
Genticamente programados parareconocer un antgeno especfico pormedio de su receptor especfico (TCR).
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LINFOCITOS T
Marcadores comunes:
CD2, CD7, CD3, CD28
CD4+: linfocitos T cooperadores/inductores
CD8+: linfocitos T citotxicos/supresores
CD4 y CD8 son mutuamente excluyentes
Relacin CD4 : CD8 = 2 : 1
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LINFOCITOS TMolculas de Superficie de las Th y Tc
Linfocito T
ICAM-1 y LFA-1 sonmolculas deadhesin celular
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Chapter 21, Immune System 10
T Cell Selection in the Thymus
Figure 21.7
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LINFOCITOS TComplejo Receptor de las Clulas T (TCR)
Sitio de unin del antgeno
CD3cadenas gamma,
delta y epsilon
TCR
alfa - beta
CD3
cadenas theta
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LINFOCITOS B
Representan el 10- 20% de linfocitos circulantes
Ubicados en centros germinales y folculos
linfoides de ganglios, bazo, amgdalas y tejidolinfoide asociado a mucosas
Se transforman en clulas plasmticas para lasecrecin de inmunoglobulinas
Reconocen especficamente a los antgenosmediante su complejo receptor especfico BCRcompuesto por cadenas y cadenas Ig
Marcadores especficos: CD19, CD21.
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LINFOCITOS B
CLULA PLASMTICA
Marcadores desuperficie
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Chapter 21, Immune System 14
Display a unique type of receptor that responds to a distinctantigen
Become immunocompetent before they encounter antigensthey may later attack
Are exported to secondary lymphoid tissue whereencounters with antigens occur
Mature into fully functional antigen-activated cells uponbinding with their recognized antigen
It is genes, not antigens, that determine which foreignsubstances our immune system will recognize and resist
Immunocompetent B or T cells
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Chapter 21, Immune System 15
Red
bone marrow
1
2
3
Immunocompetent ,
but st i l l naive,
lymphocyte
migrates via blood
Mature (antigen-activated)immunocompetent lymphocytescirculate continuously in thebloodstream and lymph andthroughout the lymphoid organs ofthe body.
Key: = Site of lymphocyte origin
= Site of development of immunocompetenceas B or T cells; primary lymphoid organs
= Site of antigen challenge and finaldifferentiation to activated B and T cellsImmature
lymphocytesCirculation inblood
1
1 Lymphocytes destined to become Tcells migrate to the thymus and developimmunocompetence there. B cellsdevelop immunocompetence in redbone marrow.
Thymus
Bone
marrow
Lymph nodes ,
spleen, and other
lympho id t issues
2 2 After leaving the thymus or bonemarrow as naive immunocompetentcells, lymphocytes seed the lymph
nodes, spleen, and other lymphoidtissues where the antigen challengeoccurs.
3 3
ActivatedimmunocompetentB and T cellsrecirculate in bloodand lymph
Immunocompetent B or T cells
Figure 21.8
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CLULAS CITOLITICAS NATURALES(NK)
Representan el 5 a 10% de linfocitos perifricos
Marcadores: CD2, CD56 y CD16 (receptor para
Fc de IgG) No presentan receptores especficos para los
antgenos ni inmunoglobulinas de superficie
Capacidad de lisar de clulas neoplsicas,clulas infectadas por virus y algunas clulasnormales por citotoxicidad directa odependiente de anticuerpos que se fijan a sus
receptores para Fc de IgG (ADCC)
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Marcadores de superficie
CLULAS CITOLITICAS NATURALES(NK)
Reconocen las clulas propias a
travs de un receptor que se une a
molculas clase I (C) del MHC para
inhibir sus accin citoltica
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GRANULOCITOSFagocitos PMN
Primera respuesta inflamatoria
Secretan enzimas proteolticas (mieoloperoxidasa)
Migran de la sangre a los tejidos por factoresquimiotcticosSobrevida y proliferacin inducida por IL-5
Respuestas alrgicas y contra los parsitos(citotoxicidad)
Clulas circulante que, junto con los MASTOCITOStisulares, secretan mediadores qumicos (Histamina)en las reacciones alrgicas tipo I mediadas por elentrecruzamiento de molculas IgE adheridas a losreceptores de memebrana
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CLULAS PRESENTADORAS DEANTGENOS (CPA)
Se originan a partir de progenitores comunes degranulocitos-monocitos por accin de la IL-3, GM-CSF y M-CSF
Circulan por la sangre, migran a los tejidos y sediferencian en macrfagos
Fagocitos tisulares
Segregan citoquinas, enzimas proteolticas yfactores citotxicos
Presentadoras de antgenos profesionales
Se encuentran en superficies tisulares mucosos ycutneas. Captan los antgenos y migran a losganglios linfticos
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CLULAS PRESENTADORAS DE ANTGENOSMACRFAGOS
Sistema monocito-macrofgico
Procesan y presentan el antgeno a clulas T
Producen (IL-1 e IFN-alfa)
Secretan metabolitos
txicos y enzimas
Son clulas efectoras
en algunas formas deinmunidad celular,
tal como en las reacciones
de hipersensibilidad retardada.
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CLULAS PRESENTADORAS DE ANTGENOSCLULAS DENDRTICAS y de LANGERHENAS
Presentan prolongaciones citoplasmticas
dendrticas y gran cantidad de molculas
MHC tipo II
Son excelentes
presentadores de
antgenos
Poca o ninguna capacidad fagoctica.
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CITOQUINAS
Molculas que inducen y regulan la respuestainmunitaria mediante el establecimiento deinteracciones con receptores especficos
presentes en linfocitos, monocitos, clulasinflamatorias y clulas endoteliales.
Son producidas por distintos tipos de clulas.
Efecto pleiotrpico (actan sobre muchos tiposcelulares) con accin autocrina, paracrina yendocrina.
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Chapter 21, Immune System 23
Epithelial Chemical Barriers
Epithelial membranes produce protective
chemicals that destroy microorganisms
Skin acidity (pH of 3 to 5) inhibits bacterial
growth
Sebum contains chemicals toxic to bacteria
Stomach mucosae secrete concentrated HCl
and protein-digesting enzymes Saliva and lacrimal fluid contain lysozyme
Mucus traps microorganisms that enter the
digestive and respiratory systems
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Chapter 21, Immune System 24
Surface Barriers (First Line of
Defense) Skin, mucous membranes, and their
secretions make up the first line of
defense
Keratin in the skin:
Presents a formidable physical barrier to most
microorganisms
Is resistant to weak acids and bases, bacterialenzymes, and toxins
Mucosae provide similar mechanical
barriers
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Innate immunity
Based on genetic make-up
Relies on already formed components
Rapid response: within minutes of infection
Not specific
same molecules / cells respond to a range of
pathogens
Has no memory
same response after repeated exposure
Does not lead to clonal expansion
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Innate immunity: mechanisms Mechanical barriers / surface secretion
skin, acidic pH in stomach, cilia
Humoral mechanisms
lysozymes, basic proteins, complement, interferons
Cellular defense mechanisms natural killer cells neutrophils, macrophages,, mast cells,
basophils, eosinophils
Neutrophil NK Cell MonocyteMacrophage
Basophils &Mast cells
Eosinophils
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Chapter 21, Immune System 27
Mechanism of Phagocytosis
Microbes adhere to the phagocyte
Pseudopods engulf the particle (antigen)
into a phagosome
Phagosomes fuse with a lysosome to form
a phagolysosome
Invaders in the phagolysosome are
digested by proteolytic enzymes
Indigestible and residual material is
removed by exocytosis
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Chapter 21, Immune System 28
Mechanism of Phagocytosis
Figure 21.1a, b
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Chapter 21, Immune System 29
3. Inflammation: Tissue
Response to Injury The inflammatory response is triggered
whenever body tissues are injured
Prevents the spread of damaging agents to
nearby tissues
Disposes of cell debris and pathogens
Sets the stage for repair processes
The four cardinal signs of acuteinflammation are redness, heat, swelling,
and pain
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Chapter 21, Immune System 30
Neutrophilsenter bloodfrom bonemarrow
1
2
3
4
Margination
Diapedesis
Positivechemotaxis
Capillary wallEndothelium
Basal lamina
Inflammatorychemicalsdiffusing fromthe inflamedsite act aschemotacticagents
Inflammatory Response: Phagocytic Mobilization
Figure 21.3
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Chapter 21, Immune System 31
4. Antimicrobial Proteins
Enhance the innate defenses by:
Attacking microorganisms directly
Hindering microorganisms ability to
reproduce
The most important antimicrobial proteins
are:
Interferon
Complement proteins
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Chapter 21, Immune System 32
Interferon Family
Interferons are a family of related proteins each with slightlydifferent physiological effects
Lymphocytes secrete gamma () interferon, but most other
WBCs secrete alpha () interferon
Fibroblasts secrete beta () interferon
Interferons also activate macrophages and mobilize NKs
FDA-approved alpha IFN is used:
As an antiviral drug against hepatitis C virus
To treat genital warts caused by the herpes virus
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Chapter 21, Immune System 33
20 or so proteins that circulate in the blood
in an inactive form
Proteins include C1 through C9, factors B,
D, and P, and regulatory proteins
Provides a major mechanism for
destroying foreign substances in the body
4 b. Complement
C l t P th
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Chapter 21, Immune System 34
Complement Pathways
Figure 21.5
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Chapter 21, Immune System 35
Toll-like Receptors (TLRs)
Macrophages and cells lining the
gastrointestinal and respiratory tracts bear
TLRs
TLRs recognize specific classes of
infecting microbes
Activated TLRs trigger the release of
cytokines that promote inflammation
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Chapter 21, Immune System 36
Immunity: Two Intrinsic Defense
Systems Innate (nonspecific) system responds
quickly and consists of:
First line of defense intact skin and mucosae prevent entry of
microorganisms
Second line of defense antimicrobial proteins, phagocytes, and
other cells Inhibit spread of invaders throughout the body
Inflammation is its hallmark and most important mechanism
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Chapter 21, Immune System 37
Internal Defenses (Second Line
of Defense) The body uses nonspecific cellular and chemical
devices to protect itself
1. Phagocytes
2. natural killer (NK) cells
3. Inflammatory response enlists macrophages, mast
cells, WBCs, and chemicals
4. Antimicrobial proteins in blood and tissue fluid
Harmful substances are identified by surface
carbohydrates unique to infectious organisms
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Adaptive immunity:
second line of response Based upon resistance acquired during life
Relies on genetic events and cellular growth
Responds more slowly, over few days
Is specific
each cell responds to a single epitope on an antigen
Has anamnestic memory
repeated exposure leads to faster, stronger response
Leads to clonal expansion
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Adaptive Immunity: Anatomy of the response
Nave T cells and B cells recirculate between lymph
nodes, spleen, and the blood.
Antigen is taken from site of infection to the lymph node
either by the flow of lymph or is carried by a maturing
dendritic cell that migrates along the lymphatics.
The dendritic cell presents antigen to nave T cells in the
lymph node to initiate the T cell immune response.
Activated T cells, after they have expanded in number,
leave the lymph node and go via the blood to sites of
inflammation, where they look for their antigen to
mediate cell-mediated immunity.
I i T I i i D f
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Chapter 21, Immune System 40
Immunity: Two Intrinsic Defense
Systems
Adaptive (specific) defense system
Third line of defense mounts attack against
particular foreign substances
Takes longer to react than the innate system
Works in conjunction with the innate system
Ad ti (S ifi ) D f (Thi d Li
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Chapter 21, Immune System 41
The adaptive immune system is a
functional system that:
Recognizes specific foreign substances
Acts to immobilize, neutralize, or destroy
foreign substances
Amplifies inflammatory response and
activates complement
Adaptive (Specific) Defenses (Third Line
of Defense)
Adaptive Immune Defenses
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Chapter 21, Immune System 42
The adaptive immune system is antigen-
specific, systemic, and has memory
It has two separate but overlapping arms
Humoral, or antibody-mediated (B Cell)
immunity
Cellular, or cell-mediated (T Cell) immunity
Adaptive Immune Defenses
Adaptive Immunity:
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Adaptive Immunity:
active and passive
Active Immunity Passive Immunity
Natural clinical, sub-clinical
infection
via breast milk,
placenta
Artificial Vaccination:
Live, killed, purified
antigen vaccine
immune serum,
immune cells
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Adaptive immunity: mechanisms
Cell-mediated immune response (CMIR)
T-lymphocytes
eliminate intracellular microbes that survive
within phagocytes or other infected cells
Humoral immune response (HIR)
B-lymphocytes
mediated by antibodies eliminate extra-cellular
microbes and their toxins Plasma cell(Derived from B-lymphocyte,produces antibodies)
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Adaptive Immunity: Antibodies I
We can make millions or billions of different
antibodies, each highly specific for a singlemolecule (ideally a pathogen molecule)
As it develops, each B lymphocyte alters its DNA
so it makes ONE antibody; each B lymphocyte isan individual, its antibody is unique
A molecule that induces the production of an
antibody is called an antigen
In a normal immune response, several B cellsthat make antibodies that recognize the infectious
agent become activated, each multiply to form a
clone. These progeny then become antibody-secretin factories.
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Adaptive Immunity: Antibodies II
Often, B cells are helped by T lymphocytes which alsorecognize the pathogen, these B cells take longer to makeantibodies, but make higher quality antibodies (bind morestrongly). Some of these high quality-producing B cellsturn into antibody-secreting factories that go to the bone
marrow and last a very long time (years). The antibodythey produce can protect us immediately when thatinfectious agent returns and prevent noticeable illness
This type of high quality/long lasting immune response(germinal center response) is the mechanism behindalmost all successful vaccines; understanding thisprinciple was used to greatly improve a class of vaccinesagainst bacterial pathogens, resulting in the conjugate
vaccines (starting in the 1990s)
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Adaptive Immunity: Cell-mediated immunity I
T lymphocytes recognize small pieces of proteins (peptides)
associated with our own cells. They do this with the T cell antigen receptor orTCR which is like
an antibody, but always on the surface of the T cell, neversecreted.
Therefore the T cell only functions locally next to cells that that
have its antigen. As with B cells, T cells alter their DNA such that each T cell makesa unique TCR and different T cells recognize different antigens
There are two types of T cells: helper T cells and killer (orcytotoxic) T cells
Helper T cells express a molecule called CD4 and are the cells thatare infected by HIV-1; their depletion leads to theimmunodeficiency of AIDS
Cytotoxic T cells express a similar molecule called CD8
Antigens
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Chapter 21, Immune System 48
Substances that can mobilize the immune
system and provoke an immune response
The ultimate targets of all immune
responses are mostly large, complex
molecules not normally found in the body
(nonself)
Antigens
Complete Antigens
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Chapter 21, Immune System 49
Important functional properties:
Immunogenicity the ability to stimulate
proliferation of specific lymphocytes and
antibody production Reactivity the ability to react with the
products of the activated lymphocytes and the
antibodies released in response to them
Complete antigens include foreign protein,
nucleic acid, some lipids, and large
polysaccharides
Complete Antigens
Haptens (Incomplete Antigens)
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Chapter 21, Immune System 50
Small molecules, such as peptides,
nucleotides, and many hormones,
not immunogenic (does not stimulate a response)
reactive when attached to protein carrier.
If they link up with the bodys proteins, the
adaptive immune system may recognizethem as foreign and mount a harmful
attack (allergy)
Haptens (Incomplete Antigens)
Antigenic Determinants
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Chapter 21, Immune System 51
Only certain parts of an entire antigen are immunogenic
Antibodies and activated lymphocytes bind to theseantigenic determinants
Most naturally occurring antigens have numerousantigenic determinants that:
Mobilize several different lymphocyte populations
Form different kinds of antibodies against it
Large, chemically simple molecules (e.g., plastics) havelittle or no immunogenicity
Antigenic Determinants
Antigenic Determinants
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Chapter 21, Immune System 52
Antigenic Determinants
Figure 21.6
Self-Antigens: MHC Proteins
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Chapter 21, Immune System 53
Our cells are dotted with protein molecules (self-
antigens) that are not antigenic to us but are strongly
antigenic to others (reason for transplant rejection)
One type of these, MHC proteins, mark a cell as self
The two classes of MHC proteins are:
Class I MHC proteins found on virtually all bodycells
Class II MHC proteins found on certain cells in the
immune response
Self-Antigens: MHC Proteins
MOLCULAS DE
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MOLCULAS DEHISTOCOMPATIBILIDAD
Molculas glucoproteicas de la superficie de lasclulas que se unen a fragmentos peptdicos, afin de presentarlos a las clulas T especficas
Son importantes en el rechazo de transplantes yen la predisposicin a enfermedades
Varios genes codifican antgenos de
histocompatibilidad, pero los principales seubican en el brazo corto del cromosoma 6 en elComplejo mayor de histocompatibilidad (MHC)
CATEGORIAS DEL COMPLEJO MAYOR
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CATEGORIAS DEL COMPLEJO MAYORDE HISTOCOMPATIBILIDAD (MHC)
Genes clase I (HLA-A, HLA-B y HLA-C) yII (HLA-DR, HLA-DQ y HLA-DP) codificanglucoprotenas de superficie celular.
Genes clase III codifican componentesdel sistema del complemento.
CLASE II CLASE III CLASE ICITO-QUINAS
B C ATNFComplemento
DP DQ DR
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CITOQUINAS
Molculas que inducen y regulan la respuestainmunitaria mediante el establecimiento deinteracciones con receptores especficos
presentes en linfocitos, monocitos, clulasinflamatorias y clulas endoteliales.
Son producidas por distintos tipos de clulas.
Efecto pleiotrpico (actan sobre muchos tiposcelulares) con accin autocrina, paracrina yendocrina.
CITOQUINAS
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Citoquinas pro-inflamatorias que median lainmunidad natural:
(IL-1, TNF-alfa, IFN-gamma, IL-8).
Citoquinas que regulan el crecimiento,activacin y diferenciacin de los linfocitos(IL-2, IL-4, IL-10, IL-12 y TGF-beta).
Ciroquinas que estimulan a otras clulas(IL-13 a linfocitos B, IL-5 a eosinfilos)
Citoquinas que estimulan la hematopoyesis
(GM-CSF, M-CSF, IL-3).
CITOQUINASClasificacin
Humoral Immunity Response
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Chapter 21, Immune System 58
Antigen challenge first encounter
between an antigen and a naive
immunocompetent cell
Takes place in the spleen or otherlymphoid organ
If the lymphocyte is a B cell:
The challenging antigen provokes a humoral
immune response
Antibodies are produced against the challenger
Humoral Immunity Response
Clonal Selection
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Chapter 21, Immune System 59
Clonal Selection
Figure 21.9
Fate of the Clones
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Chapter 21, Immune System 60
Most clone cells become antibody-
secreting plasma cells
Plasma cells secrete specific antibody at
the rate of 2000 molecules per second
Fate of the Clones
Fate of the Clones
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Chapter 21, Immune System 61
Secreted antibodies:
Bind to free antigens
Mark the antigens for destruction by specific
or nonspecific mechanisms
Clones that do not become plasma cells
become memory cells that can mount an
immediate response to subsequentexposures of the same antigen
Fate of the Clones
Immunological Memory
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Chapter 21, Immune System 62
Primary immune response cellular
differentiation and proliferation, which
occurs on the first exposure to a specific
antigen Lag period: 3 to 6 days after antigen
challenge
Peak levels of plasma antibody are achievedin 10 days
Antibody levels then decline
Immunological Memory
Immunological Memory
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Chapter 21, Immune System 63
Secondary immune response re-
exposure to the same antigen
Sensitized memory cells respond within hours
Antibody levels peak in 2 to 3 days at muchhigher levels than in the primary response
Antibodies bind with greater affinity, and their
levels in the blood can remain high for weeksto months
Immunological Memory
Summary of the Primary Immune Response
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Chapter 21, Immune System 64
Summary of the Primary Immune Response
Figure 21.19
P i d S d H l R
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Chapter 21, Immune System 65
Primary and Secondary Humoral Responses
Figure 21.10
Active Humoral Immunity
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Chapter 21, Immune System 66
B cells encounter antigens and produce
antibodies against them
Naturally acquired response to a bacterial or
viral infectionArtificially acquired response to a vaccine of
dead or attenuated pathogens
Vaccines spare us the symptoms of disease, and
their weakened antigens provide antigenic
determinants that are immunogenic and reactive
Active Humoral Immunity
Passive Humoral Immunity
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Chapter 21, Immune System 67
Differs from active immunity in the antibody source andthe degree of protection
B cells are not challenged by antigens
Immunological memory does not occur
Protection ends when antigens naturally degrade inthe body
Naturally acquired from the mother to her fetus via theplacenta
Artificially acquired from the injection of serum, such asgamma globulin
Passive Humoral Immunity
Types of Acquired Immunity
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Chapter 21, Immune System 68
Types of Acquired Immunity
Figure 21.11
RESPUESTA INMUNE
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RESPUESTA INMUNERECONOCIMIENTO DE ANTGENOS
Presentacin delpptido antignicoen la fosa o canalde la molculaMHC clase I a un
linfocito T CD8+ ocitotxico
CLULA PRESENTADORA DE ANTGENOSMolcula Clase II del MHC
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RESPUESTAINMUNEPRESENTACINDEL ANTGENO
Molcula Clase II del MHC
CLULA T CD4*
Presentacin del pptidoantignico por molculasMHC clase II a las clulas
T CD4+ (helper).Importancia de lasmolculas co-estimulatoriasCD28 y B7
RESPUESTA INMUNE
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RESPUESTA INMUNEINDUCCIN
Alergeno
Th 0
Th 1
Th 2
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Sntesis de las Inmunoglobulinas
El tipo de anticuerpo resultante depende del perfil de citoquinas
secretado por las clulas Th en respuesta a la presentacin del Ag
Antibodies
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Chapter 21, Immune System 73
Also called immunoglobulins
Constitute the gamma globulin portion of blood
proteins
Are soluble proteins secreted by activated B cells and
plasma cells in response to an antigen
Are capable of binding specifically with that antigen
There are five classes of antibodies: IgD, IgM, IgG, IgA,
and IgE
I l b li
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Inmunoglobulinas
Cada monmero se forma por la
unin no covalente de dos cadenaslivianas (kappa o lambda) y dos
cadenas pesadas especficas de
cada isotipo de inmunoglobulina:
IgM cadenas
IgG cadenas
IgA cadenas
IgE cadenas
IgD cadenas
Sus funciones biolgicas dependen
del fragmento Fc:
Fijacin de complemento (IgM eIgG)
Unin a receptores celulares (IgG,
IgM, IgE)
Pasaje placentario (IgG)
Pasaje a mucosas (IgA)
Antibody Targets
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Chapter 21, Immune System 75
Antibodies themselves do not destroy
antigen; they inactivate and tag it for
destruction
All antibodies form an antigen-antibody(immune) complex
Defensive mechanisms used by antibodies
are neutralization, agglutination,precipitation, and complement fixation
y g
Mechanisms of Antibody Action
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Chapter 21, Immune System 76
y
Figure 21.13
Funcin de las Inmunoglobulinas
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IgAPredominante en secreciones seromucosas(saliva, secreciones traqueo-bronquiales,vaginales, etc.)Se presenta como dmero (impide protelisis
por enzimas digestivas).IgG Principal anticuerpo de respuesta secundaria
(memoria).
Actividad anti-virus, bacterias, parsitos yalgunos hongosCruzan placenta (inmunidad pasiva trans-placentaria, 3-6 meses post-parto)
Activa complemento por va clsica.
Funcin de las Inmunoglobulinas
Funcin de las Inmunoglobulinas
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IgM Principal anticuerpo de respuesta inmuneinmediata y primariaSe presenta como pentmero en asociacincon cadena "J
Activa complemento por va csicaIgE Se une a receptores de alta afinidad en
basofilos y mastocitos
Participa en respuestas anti-helmintos ehipersensibilidad inmediata (anafilaxia)
IgD Se encuentra circulante y en la superficie delas clulas B maduras
Funcin de las Inmunoglobulinas
Cell-Mediated Immune Response
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Chapter 21, Immune System 79
Since antibodies are useless against intracellularantigens, cell-mediated immunity is needed
Two major populations of T cells mediate cellularimmunity
CD4 cells (T4 cells) are primarily helper T cells (TH) CD8 cells (T8 cells) are cytotoxic T cells (TC) that
destroy cells harboring foreign antigens
Other types of T cells are:
Suppressor T cells (TS) Memory T cells
p
Major Types of T Cells
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Chapter 21, Immune System 80
j yp
Figure 21.14
Importance of Humoral Response
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Chapter 21, Immune System 81
Soluble antibodies
The simplest ammunition of the immune
response
Interact in extracellular environments such asbody secretions, tissue fluid, blood, and lymph
p p
Importance of Cellular Response
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Chapter 21, Immune System 82
T cells recognize and respond only toprocessed fragments of antigen displayed
on the surface of body cells
T cells are best suited for cell-to-cellinteractions, and target:
Cells infected with viruses, bacteria, or
intracellular parasitesAbnormal or cancerous cells
Cells of infused or transplanted foreign tissue
p p
Class I MHC Proteins
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Chapter 21, Immune System 83Figure 21.15a
Class II MHC Proteins
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Chapter 21, Immune System 84
Figure 21.15b
T Cell Activation: Step One Antigen Binding
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Chapter 21, Immune System 85Figure 21.16
Helper T Cells (TH)
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Chapter 21, Immune System 86
H
Figure 21.17a
Helper T Cells
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Chapter 21, Immune System 87Figure 21.17b
Cytotoxic T Cell (Tc)
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Chapter 21, Immune System 88
TC cells, or killer T cells, are the only T cells that candirectly attack and kill other cells
They circulate throughout the body in search ofbody cells that display the antigen to which they
have been sensitized Their targets include:
Virus-infected cells
Cells with intracellular bacteria or parasites
Cancer cells Foreign cells from blood transfusions or transplants
Mechanisms of Tc Action
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