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8/14/2019 Basic Immunology I
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Basic Immunology I
May 20, 2008
MD3
Microbiology
Dr. K Ronquillo
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Primary Lymphoid Organs
Bone Marrow
Thymus
Spleen,Liver
Secondary Lymphoid organs
Lymph Nodes
Spleen
Tonsils
Mucosa-associated lymphoid tissue (MALT) GALTBALT
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THYMUS
Cortex: immature T
cells, epithelial
cells and
macrophagesmedulla, which
mature T cells and
Hassal corpuscles
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LYMPH NODES
most commonsite for the
production of the
adaptive immune
responseB cells:cortex
Tcells:
paracortex
Germinal centers:plasma cells
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SPLEEN
peripheral lymphoid organ: adults
primary lymphoid organ: fetal period
function?
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Spleen zones
White pulpperiarteriolar lymphatic sheath (PALS) :
T cellsMarginal zones: B cells
Primary follicles: B cells,dendritic cells
Red pulpsite of blood filtration
sinusoids
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BRONCHUS-ASSOCIATED LYMPHOUD
TISSUE (BALT)
Tonsils
lymphoid tissues under the respiratory
mucosa
types of tonsils:
1. palatine tonsils
2. lingual tonsils
3. pharyngeal tonsils ;adenoids
Lymph node swelling
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CELLS OF THE IMMUNE SYSTEM
Monocytes-macrophages
Dendritic cells
Granulocytes(polymorphonuclear leukocytes)neutrophils
Eosinophils
basophils
Lymphocytes
B lymphocytesT lymphocytes
Natural Killer cells
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Monocytes-macrophages
liver macrophages Kupffer cells
Brain macrophages Microglial cellsLung macrophages alveolar
macrophages
Macrophages in granulomas epitheloid cells
Cluster of epitheloid cells giant cells
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M & M
Stimuli: LYMPHOKINES
INTERFERON gamma
causes increased lysosomal enzyme
production
increased chemotactic abilities
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Functions of M and M
secrete mediators of inflammation
Opsonization (C3b)
PhagocytosisAntigen-presenting cells (MHC)
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DENDRITIC CELLS
also APCs
peripheral blood,
lymphoid organs
Langerhans cell:
skin
Reticulum cells:spleen and lymph
nodes
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Granulocytes
NEUTROPHILS
first cell in acute inflammation
azurophilic granules:
myeloperoxidase
hydrogen peroxide; toxic oxygen
radicals
receptors for IgG, C3b
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EOSINOPHILS
late inflammatory reactions, allergies,
parasitic infections
chemotactic factors include: histamine,
C5a, LTB4, PAF, ECF-A
Major Basic Proteins, Peroxidase
receptors for complement
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BASOPHILS
receptors for IgE
release of histamine
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B LYMPHOCYTES
differentiate into plasma cells
respond to 2 types of antigens;
a. T-cell independent antigens:
absence of CD4 Th cells
antigens are polysaccharides
b. T-cell dependent antigens;CLASS
SWITCHING
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T LYMPHOCYTES
two major types depending on their CD
proteins
Th1 cell: promote cytotoxic T-cell
(CD8+ cells) responses and delayed
hypersensitivity reactionsrecognize APC with MHC class I
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Th2 cell: stimulate B cells to proliferate
-differentiate into antibody
producing cells
Both Th1 and Th2 have CD4+ proteins;
recognize APC with MHC class II
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NATURAL KILLER CELLS
kill tumor cells and viruses without the
need for MHC
mediate ADCC (antibody-mediated
cellular cytotoxicity)
activated by interferon gamma and
IL-2
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THE IMMUNE RESPONSE
Innate immunity
Acquired ImmunityHumoral immune response
Cellular immune response
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ANTIGENS
any substance which is bounded by
an antibody or T cell receptor
Immunogen: a substance that
induces a specific immune response
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Hapten
non-immunogenic
Have to be coupled to a carrier
molecule
have the property of antigenicity but
not immunogenicity
Example: penicillin
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Factors which contribute to
immunogenicity
the immune system normally recognize foreignsubstances
the larger the molecule, the more antigenic it is
the more complex the structure, especiallyproteins
lipids are usually not immunogenic
polysaccharides are also good immunogens
nucleic acids are poor immunogens
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HLA CLASS I
found on all the surfaces of nucleatedcells and platelets
present them to CD8+ cytotoxic Tcells.
HLA-A, HLA-B AND HLA-C
recognize cells which have beeninfected by viruses, bacteria,parasites and tumors
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HLA CLASS II
found only on the cell surfaces of:
dendritic cellsLangerhans cells
activated macrophages
B cellsthymic epithelial cells
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HLA Class II
antigen recognition by T helper cells
(CD4+ cells)
HLA-DP, HLA-DQ, HLA-DR
recognizes cell which have been
infected by bacteria, parasites or
injected proteins
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IgG gamma heavy chains
IgA alpha heavy chains
IgM mu heavy chainsIgE epsilon chains
IgD delta chains
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Functional parts of the
Immunoglobulin
Fab fragment : portion which bind the
antigen
Fc fragment portion which binds
complement
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ANTIGEN-BINDING SITES
variable region of the light chain and
heavy chain
also called the PARATOPE
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Epitope
Antigenic Determinant
specific site on the antigen which is
recognized by the B cell or the T cell
receptor
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IgG
most versatile immunoglobulin
75% of serum Ig is IgG
only class of Ig that crosses theplacenta.
fixes complement
binding to cells like macrophages,monocytes, PMN's and some
lymphocytes: Fc receptors
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IgA
2nd most common serum Ig.
major class of Ig in secretions
local (mucosal) immunity.
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IgD
primarily found on B cell surfaces
functions as a receptor for antigen
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IgE
least common serum Ig
allergic reactions
parasitic helminth diseasesIgE does not fix complement
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ACQUIRED IMMUNE RESPONSE
: Humoral type
1. PRIMARY IMMUNE RESPONSE
first response to antigenic stimuli
no antibodies can be measured in the1st 3 to 5 days
IgM: first detected
class switching: IgG predominates
IgA:oral or mucosal antigens
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ACQUIRED IMMUNE RESPONSE
: Humoral type
2. SECONDARY IMMUNE
RESPONSE
memory or anamnestic response
memory B and T cells
IgA
IgE: helminths
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ACQUIRED IMMUNE RESPONSE
: Cellular type
major cell type : T cell
APC present the antigens to Th cells (MHCII),
secrete cytokines and IFN- gammaproliferation, differentiation of CTL,macrophages
CTL will bind to cells infected by viruses or
tumors (MHC Class I)enzymes are secreted which kill the cells
CD4+ cells activate NK cells ormacrophages and neutrophils
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Immunosuppression
active immunologic unresponsiveness
IFN gamma
IL-10
X-ray and UV radiation
surgical removal of thymus, Lymphnodes and spleen
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Corticosteroids
*peripheral blood lymphopenia
*inhibit RNA and DNA synthesis*decrease macrophage responses
*decrease monocyte chemotaxis
*decrease IgG response
CYTOKINES
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CYTOKINES
Proteins
regulate immunologic and
inflammatory response in injury
resting cells do not secrete cytokines
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Cytokines
Stimulate T and B cells
Mediate signs of inflammation
Stimulate class switchingExpression of MHC I and II
Stimulate M & Ms
COMPLEMENT SYSTEM
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COMPLEMENT SYSTEM
proteins found in the blood and tissue
fluids
important in opsonization
regulation of inflammatory response
killing cells and microbes
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Two pathways
Classical Pathway
most rapid, most
efficient
antigen-antibody
complexes
Alternative pathway
activated by:
*cell wall of gram-
negative bacteria
*bacterial and plant
polysaccharides
*cobra venom factor
*endotoxins
*aggregated IgA, IgG,
IgG, IgM
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Final Product for both pathways:
Membrane attack complex
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Basic Immunology II:Immunologic techniques and
Immunization