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IMMUNOLOGY
MAN BAHADUR RANA
BPH
ACAS,NEPAL
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Immunology
• study of our protection from foreign macromolecules or
invading organisms and our responses to them.
Overview of Immune system
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Immune system and immunity
• In the battle microbial invaders and humans and other
vertebrates protection  complex array of defensive
measures  collectively Immune system.
• Immunity State of resistance or insusceptibility
exhibited by the host  toxic molecules, microorganism
and foreign cells.
Overview of Immune system
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The need of immune system
Overview of Immune system
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Immunity
Overview of Immune system
-Species
-Racial
-Individual
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Innate/Natural/Non specific Immunity
resistance with which a person is born
genetically passed
mediated by anatomic and non specific
immunological factors
provides first line of defense against infection
Level of innate immunity varies
Overview of Immune system
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Types of Innate Immunity
1. Species Immunity:
Resistance to infection varies with the species
The basic physiological, metabolic and anatomical
characteristics of a species determine the immunity.
2. Racial Immunity:
Various animals and plant breeds Marked difference in
their resistance to certain infectious diseases
Overview of Immune system
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Types of Innate Immunity
3. Individual immunity
Different individual of same species outbreak
Escape Sub clinical Develop
Disease infection disease
Overview of Immune system
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Acquired/Specific Immunity
Develops  exposed to specific pathogen or other
foreign materials.
• Second line of response (if innate fails)
• relies on mechanisms that adapt after infection
• handled by T- and B- lymphocytes
Overview of Immune system
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Types of Acquired Immunity
1. Active immunity 2. Passive immunity
Resistanceafter effective contact with an antigen
Immune response
Overview of Immune system
Humoral or antibody
mediated
Cell mediated
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1. Active Immunity
Natural active Artificial active
-Natural infections -Bacterial vaccines
-Subclinical infections -Viral vaccines
Overview of Immune system
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2. Passive immunity
transfer of preformed (ready-made) antibodies.
important role to new born and immunocompromised
individiuals.
Natural Passive Artificial passive
Maternal antibody Parenteral administr-
fetus and infants -ation of antibodies
Overview of Immune system
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Difference between active and passive immunity
Overview of Immune system
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Antigens
Proteins, nucleoproteins, polysaccharides, and some
glycolopids  vertebrate host  immune response 
specific antibody or sensitized T cells or both.
Overview of Immune system
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Types of Antigens
1. Complete antigen or immunogen
• Immunogenicity and antigenicity
• Generally high molecular weight  mostly
proteinaceous and polysaccharides.
2. Incomplete antigen or hapten
• Antigenic but not immunogenic
• Usually low molecular weight.
• carrier molecules+ hapten  immunogenic
Overview of Immune system
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Types of Antigens
Overview of Immune system
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Antigenic determinant or epitope
Discrete sites on the macromolecules recognized by
lymphocytes
Sites either on or within the antigenantibodes react.
Very small  four or five aminoacid or monosaccharide
residue
Overview of Immune system
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Heterophile antigens
• Similar in nature, if not identical, present in different
tissues of more than one species.
• Cross reacting
• Examples
RBC of blood group BE. coli
SpirocheteCardiolipin
Forssaman antigenred cells of many animals
Overview of Immune system
ANTIBODIES
• Antigen specific proteins  plasma cells
• Belong to immunoglobulin.
• Located blood and extravascular tissues,
secretions and excretions
• Bind pathogenic microorganism and their
toxins  extracellular compartments
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Structural configuration of Antibody
Dr.T.V.Rao MD 20
CLASSES (ISOTYPES) OF IMMUNOGLOBULINS
• Classes based on constant region of heavy chains
• (IgA)(IgD)(IgE)(IgG) (IgM)
• Differentiation of heavy chains
– Length of C region, location of disulfide bonds, hinge
region, distribution of carbohydrate
• Classes have different effector functions
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Different classes of Antibodies
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Immunoglobulin Classes
I. IgG
Structure: Monomer
Location: Blood, lymph, intestine
Known Functions: Enhances phagocytosis, neutralizes
toxins and viruses, protects fetus and newborn.
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Immunoglobulin Classes
II. IgM
Location: Blood, lymph, B cell surface (monomer)
Known Functions: First antibodies  in infection.
Effective against microbes
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Immunoglobulin Classes
III. IgA
Location: Secretions (tears, saliva, intestine,
milk), blood and lymph.
Known Functions: Localized protection of
mucosal surfaces. Provides immunity to infant in
digestive tract.
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Immunoglobulin Classes
IV. IgD
V. Location: B-cell surface, blood, and lymph
Known Functions: In serum function is unknown.
On B cell surface, initiate immune response.
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Immunoglobulin Classes
V. IgE
Location: Bound to mast cells and basophils
throughout body. Blood.
Known Functions: Allergic reactions. Possibly
lysis of worms.
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