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IMMUNITY
By
TEJASWINI L. ASAWE
ASSISTANT PROFESSOR
SIDHHIS INSTITUTE OF PHARMACY
THANE
IMMUNITY: DEFINITION
 Immunity is the ability of the body to protect against all
types of foreign bodies like bacteria, virus, toxic
substances which enter the body.
 Immunity is also called disease resistance.
 The lack of immunity is known as susceptibility.
 Immunity is derived from Latin word “immune” which
means free from burden.
 In this case burden refers to disease caused by
microorganisms or their toxic products.
ANTIGEN AND ANTIBODY
 Antigens –
 Any substance which invokes an immunological
response is an antigen or immunogen .
 Certain component of cell membrane act as a antigens.
 Most are proteins or large polysaccharides from a foreign
organism.
 Antibodies –
 Proteins that recognize and bind to particular antigen
with very high specificity.
TYPES OF IMMUNITY
 Any immune response or immunity involves initial
recognition of pathogen/foreign material and then a
reaction to eliminate it.
• Broadly, immunity falls into two categories:
1. Innate (inborn) immunity
a. Species immunity
b. b. Racial immunity
2. Adaptive (acquired) immunity
a. Active immunity
b. b. Passive immunity
INNATE ACQUIRED
ACTIVE (OWN
ANTIBODIES )
PASSIVE
(READYMADE
ANTIBODIES )
ARTIFICIAL
(IMMUNIZATIO
N )
NATURAL
(EXPOSURE TO
INFECTIOUS
AGENT)
NATURAL
(MATERNAL
ANTIBODIES )
ARTIFICIAL
(ANTIBODIES
FROM OTHER
SOURCESES )
IMMUNITY
1. INNATE (NON SPECIFIC OR NATURAL)
IMMUNITY
 It refers to the inborn-ability of the body to resist, and is
genetically transmitted from one generation to the next.
 This immunity offers resistance to any microorganism or
foreign material encountered by the host.
 Innate immunity lacks immunological memory, i.e., it
occurs to the same extent each time a microorganism or
foreign material is encountered.
 Innate immunity can be divided into species, racial, and
individual immunity
A. SPECIES IMMUNITY
 Species immunity (species resistance) is that in
which a disease affecting one species does not
affect the other species.
 For convenience, humans do not contract cattle
plague, chicken cholera, hog cholera, infectious
horse anemia, etc.,
 while animals are not affected by many human
diseases such as enteric fever, scarlet fever,
syphilis, gonorrhea, measles, etc.
 Diseases of skin, to which humans are quite
susceptible, are often resisted by animals because
they have more hair and thicker hides.
B. RACIAL IMMUNITY
 Racial immunity (racial resistance) is that in which various races
(breeds) (Breed is group of animals of the same species)show
marked differences in their resistance to certain infectious diseases.
 A well known example is that Brahman cattle are resistant to the
protozoan parasite responsible for tick fever in other breeds of
cattle.
 Similarly, Black Africans affected by sickle cell anaemia, a genetic
disease, are resistant to malaria while malaria affects other human
races.
 Racial immunity (racial resistance) is that in which various races
(breeds) show marked differences in their resistance to certain
infectious diseases.
 A well known example is that Brahman cattle are
resistant to the protozoan parasite responsible for tick
fever in other breeds of cattle.
 Similarly, Black Africans affected by sickle cell anemia,
a genetic disease, are resistant to malaria while malaria
affects other human races.
C. INDIVIDUAL IMMUNITY
 Having the same racial background and opportunity
for exposure, some individuals of the race
experience fewer or less severe infections than
other individuals of the same race.
 For convenience, children are more susceptible to
diseases such as measles and chicken pox, while
aged individuals are susceptible to other diseases
like pneumonia.
2. ACQUIRED (SPECIFIC OR ADAPTIVE)
IMMUNITY
 It refers to an immunity that is developed by the
host in its body after exposure to a suitable antigen
or after transfer of antibodies or lymphocytes from
an immune donor.
 Acquired immunity is highly adaptive and is capable
of specifically recognizing and selectively
eliminating foreign microorganisms and
macromolecules, i.e., antigens.
 It exhibits the following four characteristic features
that distinguish it from nonspecific (innate)
immunity:
TYPES OF ACQUIRED IMMUNITY
Acquired immunity can be obtained by the host actively or
passively and, on this basis, can be categorized as of two
types:
a. Active immunity
The active immunity is the direct response of your body
against the pathogens.
It is induced by the exposure to a foreign antigen such as
the antigen of microbes.
It is an adaptive response of the individual after contact
with specific pathogen or antigen.
In active immunity, there is active involvement of host’s own
immune system leading to the synthesis of antibodies
and/or the production of immuno-competent cells (ICCs).
B. PASSIVE IMMUNITY
• The passive immunity is the immunity conferred to
an individual by the transfer of serum or
lymphocytes from a specifically immunized
individual.
• Passive immunity is a useful method for conferring
resistance without waiting for the development of
the active immune response.
• In passive immunity, on the contrary, the antibodies
and /or the immuno-competent cells (ICCs) are
transferred from one host to another
SR
NO
Active Immunity Passive Immunity
1 Produced actively by the immune
system of the host.
Produced passively by the immune
system of the host
2 Antibody production is induced by the
infection or by immunogens
Antibodies are not produced, but
directly transferred
3 Active immunity involves both cell
mediated and humoral immunity.
Passive immunity is due to the
presence of ready-made antibodies.
4 Natural active immunity is by clinical
infection
Natural passive immunity is by the
transfer of antibodies through placenta
5 Artificial active immunity is induced
by vaccination
Artificial passive immunity is induced
by injection of antibodies
6 Active immunity is durable Passive immunity is only transient
7 Active immunity offers effective
protection against microbes.
Passive immunity is less efficient in
offering complete protection
8 Immunological memory is present Immunological memory
9 In active immunity, the subsequent
doses with the antigen causes
booster effect
In passive immunity, the subsequent
doses is less effective due to the
immune elimination
10 Negative phase may occurs Negative phase is absent
 Similarities between Active Immunity and Passive
Immunity
 1. Both active and passive immunity are acquired
immunities
 2. Both can be natural and artificial
 3. Both types of immunity involve lymphocytes
 4. The antimicrobial components in both the systems are
antibodies
 5. Both are induced by the antigens
 6. Both systems are specific
SR
NO
INNATE IMMUNITY ADAPTIVE IMMUNITY
1. Known as natural immunity Known as acquired immunity
2 Generate a non-specific immune
response
Generate a specific immune response
3 Always present in the body Generated in response to exposure to
an external factor
4 Generates a rapid response Delayed 5-6 days
5 Plasma proteins, phagocytes,
physical and chemical barriers are
the components
Humoral and cell mediated immunity
are the components
6 Temperature, pH, skin and mucous
membrane are the barriers
Lymph nodes, spleen and lymphoid
tissues are the barriers
7 Does not develop memory cells Develops memory cells
8 Possesses a less diversity, Less
potent
Possesses a higher diversity, Exhibits
a higher potency
9 Example: Redness and swelling
caused by the white blood cells
around a wound
Ex: Vaccination against a virus
CELLULAR AND HUMORAL IMMUNITY
 The lymphocytes is the basic cell responsible for
the both cellular and humoral immunity.
 Lymphocytes are found in high concentration in
lymph nodes , spleen , at the site they are
manufactured and processed(bone marrow and
thymus) .
 They are classified as
 Primary or Central lymphoid organs –
 Bone marrow and thymus .
 Secondary or peripheral lymphoid organs –
 Lump node, spleen, adenoids, tonsils, appendix
etc.
 Many lymphocytes pass through the thymus and
processed by hormonal microenvironment.
 The lymphocytes are now called thymus derived
lymphocytes or T-Lymphocytes.
 The bone marrow derived lymphocytes do not
enter and processed by the thymus are called
B- cells.
 B- lymphocytes respond to antigen while T-
lymphocytes are responsible for cell mediated
immunity.
DIFFERENCE BETWEEN T-CELLS AND B- CELLS
Sr no Characteristics T-cells B- cells
1 Site of production Thymus Bursal
equivalent
tissue
2 Types of immunity Cell mediated Humoral
(antibody
mediated )
3 Secretory product Lymphokines Antibodies
4 Sub population Helper , killer cells Plasma cell ,
memory cells
5 Effect Against intracellular
viruses, fungi,
protozoa and cancer
cells
Against bacteria
, viruses present
in body fluids
6 Type of response Cytotoxic Precipitation ,
neutralization
The amino-terminal
portions, corresponding to
the V regions,
bind to antigen;
effector functions are
mediated by the other
domains)
VL = Variable region on
light
chain,
VH = variable region on
heavy chain,
CH = constant region on
heavy chain,
CL = Constant
region on light chain.
Structure of immunoglobulin's
STRUCTURE OF IMMUNOGLOBULIN'S
 Immunoglobulin's are heterodimers containing four peptide
chains as their basic unit.
 They are composed of two identical light chains (23kD) and
two identical heavy chains (50-70kD).
 Each light chain is bound to a heavy chain by a disulfide
bond, and by noncovalent interactions as salt linkages,
hydrogen bonds, and hydrophobic bonds, to form a
heterodimer (H-L).
 Similar noncovalent interactions and disulfide bridges link the
two identical heavy and light (H-L) chain combinations to each
other to form the basic four-chain (H-L)2 antibody structure, a
dimer of dimers.
 When the amino acid sequences of many different heavy
chains and light chains were compared, it became clear that
both the heavy and light chain could be divided into two
regions based on variability in the amino acid sequences.
STRUCTURE OF IMMUNOGLOBULIN'S
 All Immunoglobulin molecules basically consist of
 Two identical heavy chains and
 Two identical light chains
 Held together by disulfide linkage (Inter chain and Intra
chain) and non- covalent interactions.
 It is Y shaped tetramer (H2L2).
 Each heavy chains contains 450 amino acids light
chains has 212 amino acids.
IMMUNOGLOBULIN'S
 Specialized group of protein mostly associated with Y
globulin fraction.
 Immunoglobulin is a functional term while Y globulin is a
physical term.
 Abbreviated as Ig.
 Ig are produced by plasma cells in response to an antigen
and which function as antibodies.
VARIABLE AND CONSTANT REGION –
 Each chain of Ig has two region constant and
variable region.
 Light chain –
 Amino terminal is variable region (VL)
 Carboxy terminal is constant region (CL)
 Heavy chain –
 One quarter of amino terminal region is variable
region (VH).
 Remaining three quarters are constant region
(CH1) , (CH2), (CH3).
 Amino acid sequence of variable regions light and
heavy chains is responsible for specific binding of
immunoglobulin (antibody ) with antigen .
 There are certain hypervariale region mixed
between relatively invariable region.
 Light chain has 3 hypervariable regions
 Heavy chain has 4.
 The hypervariable region more specifically
determine the antigen- antibody binding .
IMMUNOGLOBULIN CLASSES
 Ig G gamma heavy chain
 Ig M mu heavy chain
 Ig A Alpha heavy chain
 Ig D Delta heavy chain
 Ig E Epsilon heavy chain
 Two types of light chain kappa (k )and lambda.
 Ig contains two kappa and 2 lambda light chains
 Kappa chain is 60 % is more common in human.
 Ig G –
 Major serum Ig is 70 – 80 %.
 Single Y shaped unit (manomer ).
 It is antibody seen in secondary immuno response
 It can transverse or cross blood vessels readily .
 Ig G is only Ig that can cross the placenta and transfer the
mothers immunity to developing fetus.
 IgG helps in bacterial immobilization.
 IgG neutralize toxin and viruses.
 Ig M –
 It is largest Ig composed of 5 Y shaped units helds together
by J polypeptide chain.
 Due to large size Ig M can not cross blood vessels hence
restricted to the blood stream.
 Ig M is first antibody to be produced in response to antigen
and most effective against microorganism.
IG A –
 Single (manomer) or double unit (diamer ) held together
by J chain .
 Mostly found in body secretions such as saliva , tears
sweat , milk, and wall of intestine .
 Ig A binds with bacterial antigen present on body surface
and remove them .
 So Ig A prevents the foreign substances from entering the
body cell.
 Ig E –
 Single Y shaped manomer
 Normally present in minute concentration in blood 0.3gm /
ml .
 Ig E levels are elevated in individuals with allergies like
hay fever , asthma.
IG D
 Ig D is single Y shaped manomer .
 Present in low concentration in circulation .
 Present on surface on B cells.
 Their function is not known.
MAJOR HISTOCOMPATIBILITY COMPLEX
(MHC)
 Group of genes that code for proteins found on the surfaces
of cells that help the immune system recognize foreign
substances.
 MHC proteins are found in all higher vertebrates.
 In human beings the complex is also called the human leukocyte
antigen (HLA) system.
 Major histocompatibility complex (MHC) is the cluster of gene
arranged within a long continuous stretch of DNA on
chromosome number 6 in Human which encodes MHC
molecules.
 MHC molecule is a cell surface glycoprotein receptor present in
APCs and acts as antigen presenting structure It plays vital role
in immune recognition, including interaction between T cells and
other cell types.
 In Human MHC is known as Human Leukocyte antigen (HLA)
complex and the genes of MHC are recognized in three classes,
consequently there are three types of MHC molecules.
TYPES OF MHC:
 Class I MHC
 Class II MHC
 Class III MHC
 MHC class-I:
 Class-I MHC gene encodes glycoprotein molecule
which expressed on the surface of all nucleated
cells and platelets.
 MHC-I molecule contains a 45KDa α-chain
associated non-covalentely with a 12KDa β2
microglobulin molecule.
 Association of α-chain and β2 microglobulin is
required for expression of class-I MHC molecule
Α-CHAIN OF MHC-I:
 The α-chain is a transmembrane glycoprotein encoded by
polymorphic gene within A, B and C region of Human HLA
complex
 The α-chain is anchored in the plasma membrane by its
hydrophobic trans-membrane segment and hydrophilic
cytoplasmic tail.
 α-chain is made up of 3 domains (α1,α2 and α3). Each
domain containing approximately 90 amino acids, a
transmsmbrane domain of about 25 hydrophobic amino
acids followed by short stretch of charged (hydrophilic)
amino acids of cytoplasmic tails of 3o amino acids.
 It can binds antigen of 8-10 animo acids long.
 α3 and β2 are organized into β-pleated sheets, each formed
by antiparallel β-strand of amino acids, this structure is
known as immunoglobulin fold.
 Because of this structure α-chain and β2 microglobulin are
classified as member of immunoglobulin super-family
receptor.
Β2 MICROGLOBULIN OF MHC-I
 β2 microglobulin is a protein encoded by a highly
conserved gene located on different chromosome
 β2 microglobulin is similar in size and organization to α3
domain.
 Β2 microglobulin does not contain transmembrane
region and is non-covalently linked with α-chain.
 Functions of MHC class I:
 Major function of MHC-I is to bind peptide antigens and
present to CD8+ T cells (T helper cells)
 CD8 T cells are specific for MHC-I antigen
 MHC-I binds endogenous antigen and present to T
helper cells.
 MHC-I molecules are found on surface of all nucleated
cells.

MHC CLASS-II:
 Class-II MHC is the glycoprotein molecule expressed
primarily on antigen presenting cells such as macrophages,
dendritic cells and B-cells.
 MHC-II molecules contains two different polypeptide chains,
1 33 KDa α-chain and 28KDa β-chain which are associated
by non-covalent interactions.
 α-chain and β-chain of MHC-II:
 α-chain and β-chain of MHC-II is a membrane bound
glycoprotein that contains external domains,
atransmembrane segment and acytoplasmic tail.
 α-chain and β-chain are made up of two domains (α1 and
α2) and (β1 and β2) respectively.
 The peptide biding cleft is a open ended groove formed
between α-chain and β-chain at proximal end. The cleft can
bind antigenic peptide of 13-18 aminoacids long.
 Functions of MHC class II:
 Major function of MHC-II is to bind peptide antigen
and present to CD4 T cells.
 MHC-II are found on surface of Antigen presenting
cells (APCs).
 CD4+T-cells are specific for MHC-II
 Activates B cells for antibody production
 MHC-II plays a significant role in graft versus host
response and in mixed lymphocyte reaction (MLR)
because the immune response gene is identical to
MHC-II in human.
MHC CLASS-III:
 MHC-III are diverse group of molecules that serves
a wide variety of functions in immune system.
 MHC-III are not a marker on cell surface.
 Functions of MHC class-III:
 Involved in complement activation
 Involved in inflammation caused by cytokines,
tumor necrosis factors etc
THANK YOU

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IMMUNITY.pptx

  • 1. IMMUNITY By TEJASWINI L. ASAWE ASSISTANT PROFESSOR SIDHHIS INSTITUTE OF PHARMACY THANE
  • 2. IMMUNITY: DEFINITION  Immunity is the ability of the body to protect against all types of foreign bodies like bacteria, virus, toxic substances which enter the body.  Immunity is also called disease resistance.  The lack of immunity is known as susceptibility.  Immunity is derived from Latin word “immune” which means free from burden.  In this case burden refers to disease caused by microorganisms or their toxic products.
  • 3. ANTIGEN AND ANTIBODY  Antigens –  Any substance which invokes an immunological response is an antigen or immunogen .  Certain component of cell membrane act as a antigens.  Most are proteins or large polysaccharides from a foreign organism.  Antibodies –  Proteins that recognize and bind to particular antigen with very high specificity.
  • 4. TYPES OF IMMUNITY  Any immune response or immunity involves initial recognition of pathogen/foreign material and then a reaction to eliminate it. • Broadly, immunity falls into two categories: 1. Innate (inborn) immunity a. Species immunity b. b. Racial immunity 2. Adaptive (acquired) immunity a. Active immunity b. b. Passive immunity
  • 5. INNATE ACQUIRED ACTIVE (OWN ANTIBODIES ) PASSIVE (READYMADE ANTIBODIES ) ARTIFICIAL (IMMUNIZATIO N ) NATURAL (EXPOSURE TO INFECTIOUS AGENT) NATURAL (MATERNAL ANTIBODIES ) ARTIFICIAL (ANTIBODIES FROM OTHER SOURCESES ) IMMUNITY
  • 6. 1. INNATE (NON SPECIFIC OR NATURAL) IMMUNITY  It refers to the inborn-ability of the body to resist, and is genetically transmitted from one generation to the next.  This immunity offers resistance to any microorganism or foreign material encountered by the host.  Innate immunity lacks immunological memory, i.e., it occurs to the same extent each time a microorganism or foreign material is encountered.  Innate immunity can be divided into species, racial, and individual immunity
  • 7. A. SPECIES IMMUNITY  Species immunity (species resistance) is that in which a disease affecting one species does not affect the other species.  For convenience, humans do not contract cattle plague, chicken cholera, hog cholera, infectious horse anemia, etc.,  while animals are not affected by many human diseases such as enteric fever, scarlet fever, syphilis, gonorrhea, measles, etc.  Diseases of skin, to which humans are quite susceptible, are often resisted by animals because they have more hair and thicker hides.
  • 8. B. RACIAL IMMUNITY  Racial immunity (racial resistance) is that in which various races (breeds) (Breed is group of animals of the same species)show marked differences in their resistance to certain infectious diseases.  A well known example is that Brahman cattle are resistant to the protozoan parasite responsible for tick fever in other breeds of cattle.  Similarly, Black Africans affected by sickle cell anaemia, a genetic disease, are resistant to malaria while malaria affects other human races.  Racial immunity (racial resistance) is that in which various races (breeds) show marked differences in their resistance to certain infectious diseases.
  • 9.  A well known example is that Brahman cattle are resistant to the protozoan parasite responsible for tick fever in other breeds of cattle.  Similarly, Black Africans affected by sickle cell anemia, a genetic disease, are resistant to malaria while malaria affects other human races.
  • 10. C. INDIVIDUAL IMMUNITY  Having the same racial background and opportunity for exposure, some individuals of the race experience fewer or less severe infections than other individuals of the same race.  For convenience, children are more susceptible to diseases such as measles and chicken pox, while aged individuals are susceptible to other diseases like pneumonia.
  • 11. 2. ACQUIRED (SPECIFIC OR ADAPTIVE) IMMUNITY  It refers to an immunity that is developed by the host in its body after exposure to a suitable antigen or after transfer of antibodies or lymphocytes from an immune donor.  Acquired immunity is highly adaptive and is capable of specifically recognizing and selectively eliminating foreign microorganisms and macromolecules, i.e., antigens.  It exhibits the following four characteristic features that distinguish it from nonspecific (innate) immunity:
  • 12. TYPES OF ACQUIRED IMMUNITY Acquired immunity can be obtained by the host actively or passively and, on this basis, can be categorized as of two types: a. Active immunity The active immunity is the direct response of your body against the pathogens. It is induced by the exposure to a foreign antigen such as the antigen of microbes. It is an adaptive response of the individual after contact with specific pathogen or antigen. In active immunity, there is active involvement of host’s own immune system leading to the synthesis of antibodies and/or the production of immuno-competent cells (ICCs).
  • 13. B. PASSIVE IMMUNITY • The passive immunity is the immunity conferred to an individual by the transfer of serum or lymphocytes from a specifically immunized individual. • Passive immunity is a useful method for conferring resistance without waiting for the development of the active immune response. • In passive immunity, on the contrary, the antibodies and /or the immuno-competent cells (ICCs) are transferred from one host to another
  • 14. SR NO Active Immunity Passive Immunity 1 Produced actively by the immune system of the host. Produced passively by the immune system of the host 2 Antibody production is induced by the infection or by immunogens Antibodies are not produced, but directly transferred 3 Active immunity involves both cell mediated and humoral immunity. Passive immunity is due to the presence of ready-made antibodies. 4 Natural active immunity is by clinical infection Natural passive immunity is by the transfer of antibodies through placenta 5 Artificial active immunity is induced by vaccination Artificial passive immunity is induced by injection of antibodies 6 Active immunity is durable Passive immunity is only transient 7 Active immunity offers effective protection against microbes. Passive immunity is less efficient in offering complete protection 8 Immunological memory is present Immunological memory 9 In active immunity, the subsequent doses with the antigen causes booster effect In passive immunity, the subsequent doses is less effective due to the immune elimination 10 Negative phase may occurs Negative phase is absent
  • 15.  Similarities between Active Immunity and Passive Immunity  1. Both active and passive immunity are acquired immunities  2. Both can be natural and artificial  3. Both types of immunity involve lymphocytes  4. The antimicrobial components in both the systems are antibodies  5. Both are induced by the antigens  6. Both systems are specific
  • 16. SR NO INNATE IMMUNITY ADAPTIVE IMMUNITY 1. Known as natural immunity Known as acquired immunity 2 Generate a non-specific immune response Generate a specific immune response 3 Always present in the body Generated in response to exposure to an external factor 4 Generates a rapid response Delayed 5-6 days 5 Plasma proteins, phagocytes, physical and chemical barriers are the components Humoral and cell mediated immunity are the components 6 Temperature, pH, skin and mucous membrane are the barriers Lymph nodes, spleen and lymphoid tissues are the barriers 7 Does not develop memory cells Develops memory cells 8 Possesses a less diversity, Less potent Possesses a higher diversity, Exhibits a higher potency 9 Example: Redness and swelling caused by the white blood cells around a wound Ex: Vaccination against a virus
  • 17. CELLULAR AND HUMORAL IMMUNITY  The lymphocytes is the basic cell responsible for the both cellular and humoral immunity.  Lymphocytes are found in high concentration in lymph nodes , spleen , at the site they are manufactured and processed(bone marrow and thymus) .  They are classified as  Primary or Central lymphoid organs –  Bone marrow and thymus .  Secondary or peripheral lymphoid organs –  Lump node, spleen, adenoids, tonsils, appendix etc.
  • 18.  Many lymphocytes pass through the thymus and processed by hormonal microenvironment.  The lymphocytes are now called thymus derived lymphocytes or T-Lymphocytes.  The bone marrow derived lymphocytes do not enter and processed by the thymus are called B- cells.  B- lymphocytes respond to antigen while T- lymphocytes are responsible for cell mediated immunity.
  • 19. DIFFERENCE BETWEEN T-CELLS AND B- CELLS Sr no Characteristics T-cells B- cells 1 Site of production Thymus Bursal equivalent tissue 2 Types of immunity Cell mediated Humoral (antibody mediated ) 3 Secretory product Lymphokines Antibodies 4 Sub population Helper , killer cells Plasma cell , memory cells 5 Effect Against intracellular viruses, fungi, protozoa and cancer cells Against bacteria , viruses present in body fluids 6 Type of response Cytotoxic Precipitation , neutralization
  • 20. The amino-terminal portions, corresponding to the V regions, bind to antigen; effector functions are mediated by the other domains) VL = Variable region on light chain, VH = variable region on heavy chain, CH = constant region on heavy chain, CL = Constant region on light chain. Structure of immunoglobulin's
  • 21. STRUCTURE OF IMMUNOGLOBULIN'S  Immunoglobulin's are heterodimers containing four peptide chains as their basic unit.  They are composed of two identical light chains (23kD) and two identical heavy chains (50-70kD).  Each light chain is bound to a heavy chain by a disulfide bond, and by noncovalent interactions as salt linkages, hydrogen bonds, and hydrophobic bonds, to form a heterodimer (H-L).  Similar noncovalent interactions and disulfide bridges link the two identical heavy and light (H-L) chain combinations to each other to form the basic four-chain (H-L)2 antibody structure, a dimer of dimers.  When the amino acid sequences of many different heavy chains and light chains were compared, it became clear that both the heavy and light chain could be divided into two regions based on variability in the amino acid sequences.
  • 22. STRUCTURE OF IMMUNOGLOBULIN'S  All Immunoglobulin molecules basically consist of  Two identical heavy chains and  Two identical light chains  Held together by disulfide linkage (Inter chain and Intra chain) and non- covalent interactions.  It is Y shaped tetramer (H2L2).  Each heavy chains contains 450 amino acids light chains has 212 amino acids.
  • 23. IMMUNOGLOBULIN'S  Specialized group of protein mostly associated with Y globulin fraction.  Immunoglobulin is a functional term while Y globulin is a physical term.  Abbreviated as Ig.  Ig are produced by plasma cells in response to an antigen and which function as antibodies.
  • 24. VARIABLE AND CONSTANT REGION –  Each chain of Ig has two region constant and variable region.  Light chain –  Amino terminal is variable region (VL)  Carboxy terminal is constant region (CL)  Heavy chain –  One quarter of amino terminal region is variable region (VH).  Remaining three quarters are constant region (CH1) , (CH2), (CH3).
  • 25.  Amino acid sequence of variable regions light and heavy chains is responsible for specific binding of immunoglobulin (antibody ) with antigen .  There are certain hypervariale region mixed between relatively invariable region.  Light chain has 3 hypervariable regions  Heavy chain has 4.  The hypervariable region more specifically determine the antigen- antibody binding .
  • 26. IMMUNOGLOBULIN CLASSES  Ig G gamma heavy chain  Ig M mu heavy chain  Ig A Alpha heavy chain  Ig D Delta heavy chain  Ig E Epsilon heavy chain  Two types of light chain kappa (k )and lambda.  Ig contains two kappa and 2 lambda light chains  Kappa chain is 60 % is more common in human.
  • 27.  Ig G –  Major serum Ig is 70 – 80 %.  Single Y shaped unit (manomer ).  It is antibody seen in secondary immuno response  It can transverse or cross blood vessels readily .  Ig G is only Ig that can cross the placenta and transfer the mothers immunity to developing fetus.  IgG helps in bacterial immobilization.  IgG neutralize toxin and viruses.  Ig M –  It is largest Ig composed of 5 Y shaped units helds together by J polypeptide chain.  Due to large size Ig M can not cross blood vessels hence restricted to the blood stream.  Ig M is first antibody to be produced in response to antigen and most effective against microorganism.
  • 28. IG A –  Single (manomer) or double unit (diamer ) held together by J chain .  Mostly found in body secretions such as saliva , tears sweat , milk, and wall of intestine .  Ig A binds with bacterial antigen present on body surface and remove them .  So Ig A prevents the foreign substances from entering the body cell.  Ig E –  Single Y shaped manomer  Normally present in minute concentration in blood 0.3gm / ml .  Ig E levels are elevated in individuals with allergies like hay fever , asthma.
  • 29. IG D  Ig D is single Y shaped manomer .  Present in low concentration in circulation .  Present on surface on B cells.  Their function is not known.
  • 30.
  • 31. MAJOR HISTOCOMPATIBILITY COMPLEX (MHC)  Group of genes that code for proteins found on the surfaces of cells that help the immune system recognize foreign substances.  MHC proteins are found in all higher vertebrates.  In human beings the complex is also called the human leukocyte antigen (HLA) system.  Major histocompatibility complex (MHC) is the cluster of gene arranged within a long continuous stretch of DNA on chromosome number 6 in Human which encodes MHC molecules.  MHC molecule is a cell surface glycoprotein receptor present in APCs and acts as antigen presenting structure It plays vital role in immune recognition, including interaction between T cells and other cell types.  In Human MHC is known as Human Leukocyte antigen (HLA) complex and the genes of MHC are recognized in three classes, consequently there are three types of MHC molecules.
  • 32. TYPES OF MHC:  Class I MHC  Class II MHC  Class III MHC  MHC class-I:  Class-I MHC gene encodes glycoprotein molecule which expressed on the surface of all nucleated cells and platelets.  MHC-I molecule contains a 45KDa α-chain associated non-covalentely with a 12KDa β2 microglobulin molecule.  Association of α-chain and β2 microglobulin is required for expression of class-I MHC molecule
  • 33.
  • 34. Α-CHAIN OF MHC-I:  The α-chain is a transmembrane glycoprotein encoded by polymorphic gene within A, B and C region of Human HLA complex  The α-chain is anchored in the plasma membrane by its hydrophobic trans-membrane segment and hydrophilic cytoplasmic tail.  α-chain is made up of 3 domains (α1,α2 and α3). Each domain containing approximately 90 amino acids, a transmsmbrane domain of about 25 hydrophobic amino acids followed by short stretch of charged (hydrophilic) amino acids of cytoplasmic tails of 3o amino acids.  It can binds antigen of 8-10 animo acids long.  α3 and β2 are organized into β-pleated sheets, each formed by antiparallel β-strand of amino acids, this structure is known as immunoglobulin fold.  Because of this structure α-chain and β2 microglobulin are classified as member of immunoglobulin super-family receptor.
  • 35. Β2 MICROGLOBULIN OF MHC-I  β2 microglobulin is a protein encoded by a highly conserved gene located on different chromosome  β2 microglobulin is similar in size and organization to α3 domain.  Β2 microglobulin does not contain transmembrane region and is non-covalently linked with α-chain.  Functions of MHC class I:  Major function of MHC-I is to bind peptide antigens and present to CD8+ T cells (T helper cells)  CD8 T cells are specific for MHC-I antigen  MHC-I binds endogenous antigen and present to T helper cells.  MHC-I molecules are found on surface of all nucleated cells. 
  • 36. MHC CLASS-II:  Class-II MHC is the glycoprotein molecule expressed primarily on antigen presenting cells such as macrophages, dendritic cells and B-cells.  MHC-II molecules contains two different polypeptide chains, 1 33 KDa α-chain and 28KDa β-chain which are associated by non-covalent interactions.  α-chain and β-chain of MHC-II:  α-chain and β-chain of MHC-II is a membrane bound glycoprotein that contains external domains, atransmembrane segment and acytoplasmic tail.  α-chain and β-chain are made up of two domains (α1 and α2) and (β1 and β2) respectively.  The peptide biding cleft is a open ended groove formed between α-chain and β-chain at proximal end. The cleft can bind antigenic peptide of 13-18 aminoacids long.
  • 37.  Functions of MHC class II:  Major function of MHC-II is to bind peptide antigen and present to CD4 T cells.  MHC-II are found on surface of Antigen presenting cells (APCs).  CD4+T-cells are specific for MHC-II  Activates B cells for antibody production  MHC-II plays a significant role in graft versus host response and in mixed lymphocyte reaction (MLR) because the immune response gene is identical to MHC-II in human.
  • 38. MHC CLASS-III:  MHC-III are diverse group of molecules that serves a wide variety of functions in immune system.  MHC-III are not a marker on cell surface.  Functions of MHC class-III:  Involved in complement activation  Involved in inflammation caused by cytokines, tumor necrosis factors etc