ANTIGEN TYPES, PROPERTIES,
HAPTENS AND ADJUVANTS
INTRODUCTION
Antigen is a substances usually protein in nature and sometimes polysaccharide, that generates a specific immune response and induces the formation of a
specific antibody or specially sensitized T cell or both.
Although all antigens are recognized by specific
lymphocytes or by antibodies,only some antigen are capable of activating lymphocytes. Molecules that
stimulates immune responses are called immunogens.
ANTIGEN TYPES
Types of antigen on the basis of order of their class (Origin)
Exogenous Antigens
1. These antigen enters the body or system and start
circulating in the body fluids and trapped by the APCs(
Antigen Processing cells such as Macrophages and dendritic cells).
2. The uptakes of these exogenous antigens by APCs are
mainly mediated by the phagocytosis.
3. Examples: Bacteria, viruses, fungi etc.
4. Some antigens start out as exogenotigen and later become endogenous ( for example,
intercellular viruses).
Endogenous Antigen
1. These are body’s own cells or sub fragments or compounds or the antigenic products that are produced.
2. The endogenous antigens are processed by the
macrophages which are later accepted by the cytotoxic T-cells.
3. Endogenous antigens include xenogenic ( heterologous) Autologous and Idiotypic or Allogeneic ( homologous) antigens.
4. Examples: Blood group antigens ,HLA ( Histocompatibility Leucocyte Antigen) etc.
Autoantigens
1. An autoantigens is usually a normal protein or complex of proteins (and sometimes DNA or RNA) that is recognized by the immune system of patients suffering from a specific
autoimmune disease.
2. These antigens should not be, under normal conditions, the target of the immune system but due mainly to genetic and environmental factors the normal immunological tolerance for such an antigen has been lost in these patients.
3. Examples: Nucleoproteins, Nucleic acid etc.
Neo – Antigen ( tumor antigen)
These are the one that are present Over the surface of Tumor specific cells that have been
Transformed from the normal cells Via the process of
Mutation.
On the basis of immune response
Complete Antigen or Immunogen
1. Posses antigenic properties denovo i.e, there are able to generate an immune response by
themselves.
Incomplete Antigen or Hapten
1. These are the foreign substances, usually non- protein substances.
2. Unable to induce an immune response antigen are called Hapten.
3. Example of a Hapten is penicillin, a small molecule and is not antigenic. However , when it is combined with certain serum proteins of sensitive individuals, the resulting
molecule becomes immunogenic, activates lymphocytes and initiates a severe and sometimes fatal Allergic
reaction ( a type of immune response).
PROPERTIES OF ANTIGEN
1. The antigen should be a foreign substance to induce an immune response.
2. The antigens have a molecular mass of 14,000 to 60,00,000 Da.
3. They are mainly proteins and polysaccharide.
4. The more chemically complex they are, the more immunogenic they will be.
5. Antigens are Species – Specific.
6. The age influences the immunogenicity. Very young and very old people exhibit very low immunogenicity.
HAPTENS
1. Haptens Derived from Greek word “Haptein” which means “ To fasten”.
2. The term Hapten was first coined by Karl Landsteiner.
3. Many low molecular weight organic molecules that are not antigenic by themselves but become
antigenic if they bond to a layer carrier molecule such as a protein. These low molecular weight by itself , they require carries molecule to act as a
complete Antigen.
4. The carrier molecules is a non antigenic component and helps in provoking the immune response. Example: Serum protein such as Albumin or Globulin.
5. Loww molecular weight ( less than 10,000).
6. Haptens can react specifically with its corresponding antibody.
7. Exampless: Capsular polysaccharide of pneumococcus , Polysaccharide “C” of beta helaemolytuc streptococci,
cardiolipin antigen , etc.
8. Haptens may be complex or simple.
Complex Hapten 1. Polyvalent
2. Precipitate with specific antibodies.
Simple Haptens 1. Univalent
2. Non – Precipitate with specific antibodies.
Examples for Haptens
1. Aniline (an organic compound) and it’s derivatives (o-, m, p- benzoic acid) ( first researched Hapten).
2. Hydralazine - A blood pressure lowering drug.
3. Fluorescein – A fluorescent dye.
4. Penicillin – An antibiotic.
ADJUVANTS
1. Adjuvants are substances that when mixed with an antigen and injected with it enhance the
immunogenicity of that antigen.
2. The word adjuvants was derived from the Latin word “ Adjuvare” which means “ To help”.
3. Adjuvants are often used to boost the immune response when an antigen has low
immunogenicity or when only small amount of an
antigen are available.
4. Adjuvants may be added to a vaccine to modify the immune response.
5. The antibody response of mice to immunization
with Bovine Serum Albumin ( BSA) Can be increased five fold or more if the BSA is administered with an
adjuvant.
Commonly used Adjuvants
1. Aluminium potassium sulfate(alum) ( first Aluminium and now completely replaced by Aluminium hydroxide and Aluminium phosphate for commercial vaccines).
2. Freunds Incomplete Adjuvant ( oil in water emulsions).
3. Freunds Complete Adjuvant ( Inactivated and dried Mycobacterium tuberculosis).
4. Plant Saponins 5. Cytokines
6. Quil A ( detergent)
7. Mineral oil and food based oil ( pea nut).
Mechanism of Immune stimulation by Adjuvants 1. Extend the presence of antigen in the blood.
2. Helps the antigen presenting cells absorb antigens.
3. Activates Macrophages and lymphocytes.
4. Support the production of cytokines.
VACCINES
❑ VACCINE IS A BIOLOGICAL PREPARATION THAT PROVIDES “ACTIVE ACQUIRED IMMUNITY” TO A PARTICULAR INFECTIOUS DISEASE.
❑ VACCINES→WEAKENED OR KILLED FORM OF THE MICROBES.
❑ VACCINES CAN BE PROPHYLACTIC OR THERAPEUTIC.
❑ VACCINATION→ADMINISTRATION OF THE VACCINE.
❑ VACCINE→VARIOLAE VACCINAE , EDWARD JENNER.
TYPES OF VACCINE
1) IMMUNE SAYSTEM.
2) NEEDS TO BE VACCINATED.
3) THE BEST TECHNOLOGY TO CREATE THE VACCINE .
TYPES
❖ LIVE-ATTENUATED VACCINE .
❖ INACTIVATED VACCINES.
❖ SUBUNIT,RECOMBINANT,POLYSACCHARIDE AND CONGJUGATE VACCINES.
❖ TOXOID VACCINES.
ON THE BASIS OF:
LIVE-ATTINUATED VACCINES:
➢ LIVE VACCINES USE A WEAKENED FORM OF THE GERM THAT CAUSES A DISEASE.
➢ CREATE A STRONG AND LONG LASTING IMMUNE RESPONSE.
LIMITATIONS:
✓ THEY DON’T TRAVEL WELL.
✓ THEY CONTAIN SMALL AMOUNT OF THE WEAKENED LIVE VIRUSES .
LIVE VACCINES :
• MEASELS,MUMPS,RUBELLA (MMR-COMBAINED VACCINE).
• ROTAVIRUS.
• SMALL POX.
• CHICKEN POX.
• YELLOW FEVER.
INACTIVATED VACCINE:
❑INACTIVATED VACCINES USE THE KILLED VERSION OF THE GERM.
❑IT MAY NEES SEVERAL DOSES OVER TIME IN ORDER.
➢ HEPATITIS A.
➢ FLU.
➢ POLIO.
➢ RABIES.
SUBUNIT,RECOMBINANT,POLYSACCHARIDE&COJ UGATE VACCINE:
❑ USE SPECIFIC PIECE OF GERM LIKE ITS PROTIEN,SUGAR OR CAPSID.
❑ THEY GIVE A VERY SRONG IMMUNE RESPONSE.
❑ CAN BE USED ON ALMOST EVERYONE WHO NEEDS THEM.
❑ WE MAY NEED BOOSTER SHOT.
1) HIB DISEASE.
2) HEPATITIS B.
3) HPV.
4) WHOOPING COUGH.
TOXOID VACCINE
❑ THEY USE A TOXIN.
❑ CREATE IMMUNITY TO PART OF THE GERM.
❑ WE MAY NEED BOOSTER SHOTS.
❖ DIPTHERIA.
❖ TETANUS.
TOXOID
❑ A TOXOID IS AN INACTIVATED TOXIN.
❑ TOXINS ARE SECRETED BY BACTERIA.
❑ ANATOXIN.
❑ THEY USED AS VACCINE.
❑ TETANUS TOXOID - CLOSTRIDIUM TETANI.
ANTITOXIN
❖AN ANTITOXIN IS AN ANTIBODY WITH THE ABILITY TO NEURALIZE A SPECIFIC TOXIN.
❖ANTITOXINS ARE MADE WITH IN ORGANISMS ,INCLUDING HUMANS.
IMMUNOGLOBULIN structure and
properties
Introduction
Immunoglobulins are glycoprotein molecules that are produced by plasma cells in response to an immunogen and which function as antibodies. The
immunoglobulins derive their name from the finding that they migrate with
globular proteins when antibody-containing serum is placed in an electrical field
They are briefly represented as Ig. They are commonly called Antibodies (Ab). All antibodies are Ig, but all immunoglobulin may not be Antibodies.
They are found in the Serum, Body fluids and Tissues
They produced by Vertebrates only. They are synthesized by B lymphocyte and secreted by plasma cell.
Structure
Proposed by Rodney porter in 1962
SHAPE
Immunoglobulins are Y shaped. It has a stalk and two limbs.
The tip of the limbs is called the Antigen binding site or Paratope.
The tip of the stalk is called FC. It binds to the Phagocytes or complements.
Structure
FORMS
Its Have two type Forms I Soluble Ig
Fand in dissolved condition in the blood Serum and body fluids.
II Bound Ig
Found on the surface of B cells.
Reference to as Surface Ig. The surface Ig found on the surface of B cells is called B cell receptor(BCR).
Structure
Immnoglobulins can differ structurally, that all built from the same basic units.
1. Heavy ChainS 2. Light Chains 3. Disufide bonds
4. Variable and Constant regions 5. Hinge region
6. Domain
7. Oligosaccharides
Havey Chains
All immunoglobulins have a four chain structure as their basic unit. They are composed of two identical light chains (23kD) and two identical heavy chains (50-70kD)
2 heavy Chain – i) Longer or Havey Chain. ii) Identical
Heavy Chain is made up of 450 to 700 Amino acids
Heavy Chain have 5 type
i) Gamma ii) Alpha iii) Mu iv) Delta v) Epsilon
Light Chains
All immunoglobulins have a four chain structure as their basic unit. They are composed of two identical light chains (23kD) and two identical heavy chains (50-70kD)
2 light Chains – i) Shorter ii) Identical
Light Chains is made up of 214 Amino acids
Light Chain have 2 grouped i) Kappa ii) Lambda
Disulfide bonds
1. Inter-chain disulfide bonds - The heavy and light chains and the two heavy chains are held together by inter-chain disulfide bonds and by non-covalent interactions The number of inter-chain disulfide bonds varies among different immunoglobulin molecules.
2. Intra-chain disulfide bonds - Within each of the polypeptide chains there are also intra- chain disulfide bonds.
Variable and Constant regions
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. These are the:
1. Light Chain - VL (110 amino acids) and CL (110 amino acids)
2. Heavy Chain - VH (110 amino acids) and CH (330-440 amino acids)
Hinge region
This is the region at which the arms of the antibody molecule forms a Y. It is called the hinge region because there is some flexibility in the molecule at this point.
Oligosaccharides
Carbohydrates are attached to the CH2 domain in most immunoglobulins. However, in some cases carbohydrates may also be attached at other locations.
IMMUNOGLOBULIN FRAGMENTS
When immnoglobulin is digested with papain, a protein enzyme, the immnoglobulin splits an the hinge into two fragments namely:
1. Fab – Antigen binding fragment 2. Fc – Crystalizable fragment
Fab Fragment
Fab means Antigen binding fragment
Fab is formed of two Identical fragments. They are the limbs of the antibody
Each Fab consists of two light Chains and two heavy Chains
The heavy Chain of each Fab is made up of Vh and ChI domains
Domains
Three dimensional images of the immunoglobulin molecule show that it is not straight as depicted in figure 2A. Rather, it is folded into globular regions each of which contains an intra-chain disulfide bond (figure 2B- D). These regions are called domains.
1. Light Chain Domains - VL and CL
2. Heavy Chain Domains - VH, CH1 - CH3 (or CH4)
Fc Fragment
Fc refer to Crystalizable fragment
It is the fragment of the stalk region of the antibody
It consists of two Identical fragments
It is Made up of heavy Chain only. It contains CH2 and CH3
Properties
Immnoglobulin are glycoproteins
The molecular weight range from 1,50,000 to 9,50,000
The valency for antigen binding veries from 2 to 10. The antibodies are multivalent
The half life varies from 2 to 25 days
They contain disulfide bonds
They from precipitate with antigens
They corss placenta
They fix macrophages
Function
Agglutination of Antigen
Precipitation of Antigen
Neutralization of Antigen
Lysis of the Antigen
Tissue fixation
Phagocytosis and chemotaxis
Activation of mast cells and basophils
• Immunoglobulin
types
SERUM IgA:
Similar to IgG.
Serum level 0.6 to 4.2mg/ml.
Polypeptide chain – 2 light
and heavy chains each.
Secretory IgA:
Secretions of respiratory, urigogenital, gi tracts.
Secretory components are
synthesized by epithelial cells.
Connects 2 -IgA molecules
through fc ends.
Functions of IgM
It does not have the antibody activity .
Do not mediate any of effector functions attributed Ig.
It is associated with the surface of basophils, mast cells, activate them to secrete
antimicrobial factors to participate in
respiratory immune problems.
Functions of IgE
THEORIES OF ANTIBODY
PRODUCTION
COMPLEMENT SYSTEM
