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Presented by:
Christian Bernardes, Asher Dolina, Marycris Manuel, Genkei Parco
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Host reaction to a foreign
substance (antigen) in which this
reaction will provide protection to
the host, through recognitionand elimination of an antigen
Immune response could either be:
1. Humoral
2. Cellular
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adaptability to foreign invaders
specificity in responding to anyparticular invader
long term memory of first contactwith foreign material
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Ingested
Mode of Entry Site of Ag trapping
Peyers patchesIntestinal mucosa
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Inhaled
Mode of Entry Site of Ag trapping
Alveolar lining
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Mode of Entry Site of Ag trapping
Intracutaneous/
Subcutaneous
Regional lymph node
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Mode of Entry Site of Ag trapping
Intravenous/
Intraperitoneal
Spleen
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Cell Group Surface components Function
B-lymphocytes Surfaceimmunoglobulin
(Ag recognition)
Immunoglobulin Fc
receptor
Class II MajorHistocompatability
Complex (MHC)
(Ag presentation)
Direct antigen
recognition
Differentiation into
antibody-producing
plasma cells
Antigenpresentation within
Class II MHC
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Cell Group Surface components Function
CD3molecule
T-cell receptor (TCR,Ag recognition)
Involved in both
humoral and cell-
mediatedresponses
T-lymphocytes
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Cell Group Surface components Function
CD4molecule Recognizes antigen
presented within
Class II MHC
Promotes
differentiation of B-
cells and cytotoxic
T-cells
Activates
macrophages
Helper T-cells (TH)
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Cell Group Surface components Function
CD8molecule shut down T cell-
mediated immunity
toward the end ofan immune reaction
suppress auto-
reactive T cells that
escaped the processof negative
selection in the
thymus.
Suppressor T-cells (TS)
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Cell Group Surface components Function
CD8molecule Recognizes antigen
presented within
Class I MHC
Kills cells expressing
appropriate antigen
Cytotoxic T-cells (CTL)
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Cell Group Surface components Function
CD4 & CD8 molecule providing the immune
system with
"m
em
ory" againstpast infections.
Memory T cells
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Cell Group Surface components Function
Variable Phagocytosis and cell
killing
Accessory cells
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Cell Group Surface components Function
Variable Phagocytosis and cell
killing
Accessory cells
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Cell Group Surface components Function
Immunoglobulin Fc
receptor
Complement
component C3b
receptor
Class II MHCmolecule
Bind Fc portion of
immunoglobulin (enhances
phagocytosis)
Bind complementcomponent C3b (enhances
phagocytosis)
Antigen presentation within
Class II MHC
Secrete IL-1 (macrokine)
promoting T-cell
differentiation and
proliferation
Can be "activated" by T-cell
lymphokines
Macrophages
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Cell Group Surface components Function
Immunoglobulin Fc
receptor
Complement
component C3b
receptor
ClassII
MHCmolecule
Bind Fc portion of
immunoglobulin (enhances
phagocytosis)
Bind complementcomponent C3b (enhances
phagocytosis)
Antigen presentation within
Class II MHC
Secrete IL-1 (macrokine)
promoting T-cell
differentiation and
proliferation
Can be "activated" by T-cell
lymphokines
Macrophages
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Cell Group Surface components Function
Class II MHC
molecule
Antigen presentation
within Class II MHC
Dendritic cells
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Cell Group Surface components Function
Immunoglobulin Fc
receptor
Complement
component C3b
receptor
Bind Fc portion of
immunoglobulin
(enhancesphagocytosis)
Bind complement
component C3b
(enhancesphagocytosis)
Polymorphonuclearcells (PMNs)
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Cell Group Surface components Function
Immunoglobulin Fc
receptor
Bind Fc portion of
immunoglobulin
Kills antibody-coated
target cells (antibody-
dependent cell-
mediated
cytotoxicity, ADCC
K cells
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Cell Group Surface components Function
High affinity IgE Fc
receptors
Bind IgE and initiate
allergic responses by
release of histamine
Mast cells
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Macrophages are in a restingstate until chemicals that arereleased during an immuneresponse activate them.
Upon activation, these cellstravel toward the site ofinjury and they engulfdisease-causing organisms
Once ingested, the pathogenbecomes trapped in aphagosome, which thenfuses with a lysosome.
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Non-encapsulated microorganisms are easily
phagocytosed and killed withinmacrophages
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Encapsulated microorganisms require the production of
antibody in order to be effectively phagocytosed. Onceengulfed, however, they are easily killed.
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Intracellular microorganisms elicit the production of antibody, which
allows effective phagocytosis. Once engulfed, however, they survivewithin the phagocyte and eventually kill it.
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I
ntracellularm
icroorganism
s can also activate specific T-cells (with or without theaid of antigen presenting cell), which then release lymphokines (e.g. IFN, TNF) thatcause macrophage activation. Activated ("killer") macrophages are then veryeffective at destroying the intracellular pathogens.
IFN
TNF
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Also known as the accessory cell
displays foreign antigen complex withmajor histocompatibility complex
(MHC) on its surface.
T-cells may recognize the MHC-antigen complex using their T-cellreceptor (TCR).
These cells process antigens andpresent them to T cells.
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very efficient at internalizing antigen,either by phagocytosis or by receptor-mediated endocytosis
Present the antigen to T cells via MHC II
There are three main types ofprofessional APCs:
Dendritic cellsM
acrophagesB cells
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does not constitutively express the Majorhistocompatibility complex, class II (MHC class II)
MHC II are expressed only upon stimulation of thenon-professional APC by certain cytokines such asI
FN-.
Non-professional APCs include:
Fibroblasts (skin)Thymic epithelial cells
Thyroid epithelial cellsGlial cells (brain)Pancreatic beta cellsVascular endothelial cells
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Involves proteins called immunoglobulinor antibodies that fight against diseaseand infection.
Secreted antibodies by the B cells bind to
antigens on the surfaces of invading
microbes (such as viruses or bacteria),
which flags them for destruction.
Humoral immunity is so named because it
involves substances found in the humours,
or body fluids.
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to bind specifically to the
molecules of the foreign agent
that triggered the immune
response.
to attract other cells and
molecules to destroy thepathogen after the antibody
molecule is bound to it.
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The B cells
are induced to proliferate and produce several identical cells
capable of producing the same antibody. Cytokines also signalthe B cells to mature into antibody producing cells or plasma cells
T cells then release certain chemicals known as cytokines (orlymphokines)
The helper cells recognize the pathogen bound to the C-II
proteinT cells become activated
The antigen-antibody pair is partially digested
bound to C-II that is displayed on the surface of the B cell
Engulfed by the antigen-presenting cells
B - cells
Foreign agent enters the body
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Neutralization - antibodies bind to the bacteria or toxinand prevent it from binding and gaining entry to a host
cell.
Opsonization - binding of the antigen to the phagocyteis greatly enhanced.
Phagocytosis antibodies attract cells likemacrophages to engulf the pathogens and destroythem
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biological process that prepares antigens for
presentation to special cells of the immune
system called T-lymphocytes.
involves two distinct pathways for processing of
antigens: Endogenous and Exogenous pathway
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1
Class Imolecules bind peptides that have been synthesizedwithin the cell-viral proteins
2
Peptides from degraded viral proteins are transported intothe endoplasmic reticulum
3
Partially folded MHC Imolecules bound by calnexinmeetsviral peptide in the endoplasmic reticulum
4
Peptide binding completes MHC 1 folding, releasing calnexin;
only folded molecules are exported to the Golgi Apparatus
5
Bound viral peptide is carried by MHC class I to the cellsurface
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1 Phagocytosis or endocytosis of antigen
2
Digestion of antigen into peptide fragments (APC)
3
Fusion of vesicles containing peptide fragments and MHC IImolecules
4 Peptide fragm
ents bind to MHCII
m
olecules
5
Vesicle undergoes exocytosis and Ag-MHC II complexes areinserted into the surface of the membrane
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Antigen presentation: a process inthe body's immune system by which
macrophages, dendritic cells andother cell types capture antigensand then enable their recognition
by T-cells.
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It is important for T cell to recognize whether theantigen is in the cytosol or in the vesicularsystems.
MHC class I route presents peptides derived fromcytoplasmic antigens.
MHC class II route presents peptides derived
from extracellular or intravesicular antigens.
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Cytoplasmic proteins are degraded bythe proteasome
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Proteosome-consist of 4 stacks of 7units
-in each of the 7 units, the2 middle stacks haveproteolytic enzyme activity
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MHCI is atransmembrane proteinmade in the ER
Cytoplasm-derivedpeptides must betransported into the
ER to bind MHCI
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The invariant chain (Ii)blocks the MHCIIpeptide-binding cleftwhile it is in the ER
Acid proteases cleave Iibut leave a fragment(CLIP) in the peptide-binding groove
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First time a helper T cellinteracts with its antigen, theresponse is slow (primary
immune response).
When re-exposure to pathogento which memory cells have
been generated, little lag occur.(secondary immune response)
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First time Ag is encountered/ first injection of Ag
Lag/ delayed response of several hours to several days(Latent/Induction period)
Dependent on (1) type of Ag introduced, (2) route ofadministration. (3) species of animal (4) serological test
Ab is detected (5th to 10th day)
Rises, reaches its peak, begins to drop
Stop the production ofIgM (switch to IgG)
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Lag phase delayedresponse
Log phase increase Ab
production
Plateau phaseAb titeris stabilized
Decline phase Ab iscleared
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Accelerated/Booster/Anamnestic response
Second injection of the same Ag
Ab drops first: still complexing with newly injected Ag
Rises, reaches its peak, persist for a long period of time
Long lived cells, more Ab production, more IgG than IgM (memorycells)
Faster response because the host is primed for the particular Ag
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Differences 1o response 2o response
1. Ab titer
1. Time course (Lag phase)
1. Ab class (IgG)
1. Ab affinity
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