- 1 Immunology and the Concept of Vaccination – What is a Vaccine and its Process of Vaccination
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Immunology and the Concept of Vaccination – What is a Vaccine and its Process of Vaccination
The branch of science which deals with the study of the defensive mechanism of the body to prevent the infection of germs, formation of antibodies, and neutralization of antigens for the protection of diseases, is called immunology.
Various microscopic organisms and their secreted toxic products called antigens on entering the body produce different diseases. These microscopic organisms are called microbes or germs. The microbes enter the body through inspired air, drinking water and foods, etc. Our body has the ability to defend against the infection of germs in various ways. The body also reacts to antigens to produce antibodies that neutralize the antigens. Thus the body can protect against diseases in various ways.
Different Cells of the Immune System
- Lymphocyte: T-lymphocyte and B-lymphocyte.
- Null Cell: Killer cell or natural killer cell (NK cell).
- Mononuclear Phagocytes: There are two types monocyte and macrophage.
- Granular Leucocyte: Neutrophil, Eosinophil, Basophil.
- Mast Cells: Found in areolar connective tissue.
- Dendritic Cells: Found in various parts of the body, such as Langerhans cells in skin and mucus membrane, interdigitating dendritic cells in the medulla of the thymus gland, lungs, liver, etc.
Lymphoid Organs and Tissues
Lymphoid organs are an important part of the body’s immune system. Our body depends on the lymphoid organs for protection against invading pathogens that are responsible for various diseases. Lymphoid organs can be of 2 types, i.e., primary and secondary lymphoid organs. Lymphocytes (B and T lymphocytes) development and maturation take place in lymphoid organs.
A. Primary Lymphoid Organs:
Primary lymphoid organs are the sites of lymphocyte generation from immature progenitor cells. Thymus and bone marrow are the primary lymphoid organs.
1. Bone marrow:
Bone marrow is the principal site of blood cell formation in adults. Bone marrow generates lymphocytes from progenitor cells. Formation and maturation of all B cells & formation of T cells occur in the bone marrow.
Thymus is located within the thoracic cavity and at the lower portion of the neck. The Thymus gland is much more active and large during childhood which gradually becomes small and inactive with age. T-lymphocytes after producing from bone marrow migrate to the thymus where T-cell maturation and proliferation take place.
B. Secondary Lymphoid Organs:
Lymphocyte activation takes place in the secondary lymphoid organs. They are also known as peripheral lymphoid organs. Tonsils, lymph nodes, payer’s patch, and spleen are some examples of peripheral lymphoid organs. Mature lymphocytes circulate throughout the blood and the secondary/peripheral lymphoid organs until any foreign antigen is encountered by them. When encountered, the activation process occurs in secondary lymphoid organs.
Antigen and Antibody
When any foreign chemical or microbes are introduced into the body, the protein produced in the body can evoke an immune response in the body and causes specific reactions with the antibodies.
These are foreign substances that on entering the body stimulate the formation of antibodies and react with them. Chemically antigens are nucleoprotein, lipoprotein, glycoprotein, or large polysaccharides. The microbes or the parts of their body like capsules, flagella, and cell walls also act as antigens.
Properties of Antigen
- Chemical nature: Antigens are proteins in nature. Some antigens are polysaccharides and lipoproteinaceous, and some are simple or conjugated.
- Molecular weight: Molecular weight of the antigen is 1,000 Dalton or more.
- Specificity: The ability of an antigen to bind with specific antibodies.
- Body part specificity: Specific antigens remain in specific body parts or tissue.
- Immunogenicity: The antigen has the capacity to evoke an immune response inside the host body.
- An antigen has determinant sites for immunogenicity. An antigen must have at least two determinant sites. The part of the antibody which unites the antigen is called a paratope.
- The part of the antigen which unites with the paratope is called the epitope.
- Immunogen: These are antigens that form antibodies and react with them. But antigens are not always able to form antibodies though they react with them. So all immunogens are antigens but all antigens are not immunogens.
- Hapten: Haptens are specific chemical substances that cannot form antibodies, but can react with preformed antibodies, e.g., 5-hydroxytryptamine.
The word adjuvant comes from the Latin word adjuvant means to help. That substance enhances the immunogenic property of a substance that is not particularly antigenic. For e.g., aluminum potassium sulfate (alum) is a common adjuvant.
Types of Antigen:
The antigen is of two types-
- Exogenous antigen: The protein which is other than body protein, enters the body from outside as a pathogen is known as an exogenous antigen, e.g., pollen grain, pollutant, etc.
- Endogenous antigen: This type of antigen is produced in the body and is known as an endogenous antigen, e.g., Forssman antigen present in the red blood cells of rats, cats, sheep, horses, etc.
Antibodies are proteins that are formed by the influence of antigens in the body. The antibodies react with antigens to neutralize their effects. Antibodies are formed from G globulin protein and are called immunoglobulin.
Structure of Antibody:
Generally, each antibody is made of two pairs of polypeptide (Tetrapeptide) chains. The two chains in each pair are similar. In one pair each chain is made of 400 amino acids and is called a heavy chain (53-75 kD). In the other pair, each chain is made of 200 amino acids and is called a light chain (23 kD).
The antibody has two similar half-parts. Each half part is made of one heavy and one light chain connected by a disulphide (-S-S-) bond. The shape of the antibody molecule is more or less like ‘Y’ but sometimes is like ‘T’. The Y-shaped identical fragments form two antigen binding sites and are called fragment antigen binding = Fab. This antigen binding site binds to the specific antigen in a lock-and-key fashion forming and called antigen-antibody complex. The other fragment of Y-shaped antibody, which cannot bind antigen but become crystallized is called fragment crystalizable = Fc.
In antibodies, each polypeptide chain has one amino (-NH2) end and one carboxyl (-COOH) end. The part of the chain with the -NH2 end is called the variable or ‘V’ area. It is the antigen binding site which is different in different antibodies. The part of the chain with the -COOH end is called the constant or ‘C’ area. It is equal in all the antibodies of the same class. The ‘C’ area is responsible for the difference of the types of antigen-antibody reactions. In IgG, the ‘V’ area has two binding sites, and the ‘C’ area has one binding site. Between the first and second ‘C’ areas of the two heavy chains of antibody, there is a Hinge area. This area responds to enzyme and chemical reactions.
According to the amino acid arrangement of heavy chain and constant (c) area, the antibody or immunoglobulin is of five types-
- IgG (Gamma, γ): They are the simple type of antibodies most abundant in blood, lymph, and intestine. This type of antibody can easily cross the placenta to develop immunity to the developing foetus.
- IgA (Alpha, α): This antibody is present in all body secretions like milk, saliva, mucous, tear, etc. They can protect the body from bacteria. So this type of antibody is called secretory immunoglobulin. This antibody provides passive immunity to the newborn through colostrum and fights against local infections.
- IgM (Mu, µ): These are the largest antibody, present in blood as pentamers. They are present on the surface of B-lymphocytes, blood, and lymph. They destroy antigen-bearing cells by agglutination and bacteriolysis.
- IgD (Delta, δ): This antibody is found in the upper surface of B-lymphocyte as a monomer and in plasma cells (0.2%). They act as receptors for antigens of B-lymphocyte and are effective against allergens and toxins.
- IgE (Epsilon, ε): This antibody is found in very fewer amounts in the blood (0.1%). They are located on the mast cell and cell membrane of basophil cells and are responsible for allergic reactions.
Comparative Discussion of Five Types of Immunoglobulins:
Function of Antibody
- Agglutination: The antibodies react with germs with more than one antigen and assemble them. The process is called agglutination. The antibody which helps in the agglutination is called agglutinin, e.g., IgG, IgA.
- Precipitation: The antibody reacts with antigen and the product is precipitated. The antibody which precipitates the antigen is called precipitin, e.g., IgA, IgM.
- Neutralization: The antibody covers the toxic site of the germ to mask its effect. This type of antibody is called antitoxin, e.g., IgG.
- Lysis: Some powerful antibodies directly attack the membrane of the germ and destroy it.
- Opsonization: In this immune process, particles such as bacteria are targeted for destruction by an immune cell known as phagocyte (Neutrophil, Monocyte, Macrophage). The process of opsonization is a means of identifying the invading particle to the phagocyte.
- Complement Mediated Cell Lysis: Complement acts as enzymes which triggered by IgG and IgM, bind to the surface of foreign cells, and directly or indirectly destroy them.
In addition, other substances present in blood and the body also destroy germs.
- Enzyme: Lysozyme present in tears and saliva kills bacteria.
- Acid: HCl of gastric juice destroys germs engulfed with foods.
- Properdin: A large protein molecule that reacts with gram negative bacteria and destroys it.
- Basic polypeptide: This reacts with some gram-positive bacteria to inactivate and destroy it.
In the blood, the antigens are specifically and with high affinity bound by antibodies to form an antigen-antibody complex. The immune complex is then transported to a cellular system where it can be destroyed or deactivated. By agglutination, precipitation, lysis, neutralization, and opsonization antibody destroy the antigens.
The smallest area of antigen that is capable of binding to a particular site of antibody is called an epitope. And the corresponding area of the antibody molecule that combines with the epitope is called a paratope. The number of epitopes in an antigen determines its binding capacity of it. More than one epitope means it can bind with more than one antibody.
By two processes phagocytosis and diapedesis, bacteria or organisms are destroyed by antigens.
- Phagoqjtosls: In this process, a phagocyte cell engulfs bacteria or organisms to form an internal vesicle known as a phagosome. The phagosome of ingested material is then fused with the lysosome and leading to degradation.
- Diapedesis: Diapedesis is the movement or passage of blood cells of an injured tissue especially white blood cells, through intact capillary walls into surrounding body tissue and destroys the bacteria by phagocytosis process.
Monoclonal Antibodies and Polyclonal Antibodies
Monoclonal Antibodies (mAbs): Antibody molecules that are produced from the same type of plasma cells are called monoclonal antibodies.
Production of Monoclonal Antibodies:
Monoclonal antibodies are produced by using a technique known as hybridoma technology. Here hybridoma is a type of hybrid cell produced from the fusion of-
- Antibody-producing B-cell (hepatocytes of mice immunized with foreign antigen).
- Myeloma cell (Tumour cell), capable of multiplying infinitely.
The stepwise process of the production of monoclonal antibodies using hybridoma technology is:
- Spleen cells (hepatocytes) from mice were immunized with foreign antigens for producing a specific antibody.
- Now after some days antibody-secreting B cells were isolated from that mice.
- These B cells were then fused with myeloma cell line which is collected from a rat having tumor.
- These hybridomas or fused cells were grown and selected on HAT (Hypoxanthine-aminopterin thymidine) medium because unfused cells cannot survive on the HAT medium.
Now antibodies produced from these hybridomas are monoclonal and can be used in drug development procedures, immunoassay techniques, etc.
Polyclonal Antibodies (pAbs): Antibodies that are produced from different types of plasma cells, are called polyclonal antibodies. Polyclonal antibodies are generally purified from the serum of immunized animals. Here antigen of interest stimulated the B-lymphocytes to produce a vast range of immunoglobulins specific to that antigen.
Compared to polyclonal antibodies, the homogeneity of monoclonal antibodies is very high. Polyclonal antibodies were not useful for probing specific domains of antigen, because antiserum will usually recognize many domains. Polyclonal antibodies generate large amounts of non-specific antibodies whereas monoclonal antibodies generate specific ones.
Comparison between Monoclonal & Polyclonal Antibodies:
|Monoclonal Antibodies||Polyclonal Antibodies|
|1. Specific antibodies are produced.||1. Nonspecific antibodies are produced.|
|2. Expensive procedure.||2. Inexpensive procedure.|
|3. Time-consuming procedure.||3. Relatively less time-consuming.|
|4. Trained professionals are required for the technique to be implemented.||4. Skilled professionals are not necessary.|
|5. Able to recognize only one epitope on an antigen.||5. Can recognize multiple epitopes on an antigen.|
Difference between Antigen and Antibody:
|1. Substance||Foreign substance on entering the body stimulates the formation of antibody.||Protein substances are formed due to the entry of antigens into the body.|
|2. Nature||Chemically protein or large polysaccharide in nature.||Chemically protein in nature.|
|3. Site in the body||Remains dissolved in body fluid or cell membrane.||Remains dissolved in plasma.|
|4. Role||Produces disease in the body.||Prevents the disease in the body.|
The resistance power of the body to defend against the infection of germs to prevent the onset of diseases is called immunity.
Sir Macfarlane Burnet defines immunity as “The capacity to recognize the intrusion of material foreign to the body and to mobilize cells and cell products to help to remove that particular sort of foreign material with greater speed and effectiveness.”
Types of Immunity
Immunity is mainly of two types Innate or Inherited, Acquired Immunity.
1. Innate Immunity
This immunity, also called natural or native immunity, is present from birth by virtue of genetic constitutional makeup. It is there in the body without any external stimulation or a previous infection from outside. It is of two types:
- Specific innate immunity: It is the immunity of some races against particular diseases, e.g., Human beings never suffer from cowpox.
- Non-specific innate immunity: It is the immunity that can protect commonly all types of diseases naturally without previous relation with foreign germs, e.g., neutrophil, monocyte, and macrophage cells present in blood from birth can destroy any germ that enters the body by phagocytosis. Non-specific immunity constitutes the first line of defense.
Defence Mechanism of Innate Immunity:
- Phagocytosis: Phagocyte cell of the reticuloendothelial system, monocyte, neutrophil, kupffer cell of the liver, etc. destroys bacteria by phagocytosis.
- Add and Enzyme: The bacteria in the pancreas destroys by pancreatic HCl and enzymes.
- Skin and mucus membrane also destroys the bacteria.
- Lysozyme, basic polypeptide, properdin, antibody, natural killer cell destroys particles or organism or bacterium.
Non-specific innate immunity acts along four types of barriers i.e., physical, physiological, cellular, and cytokine, interferon barriers.
1. Physical Barriers:
They prevent the entry of any foreign substance inside the body. The most important among these are skin and mucous membranes.
- Skin: It is tough and acts as a barrier to any kind of virus and bacteria.
- Mucous Membrane: It traps the microorganisms and dust particles that may have entered the body through the respiratory tract.
2. Physiological Barriers:
pH of some body fluids, several secretions, and the temperature of the body also contribute to the protection of the body against diseases. The main physiological barriers are:
- Acid: The extremely acidic nature of gastric juice kills most of the microbes ingested with food.
- Cerumen (ear wax): It traps and prevents the entrance of dust, bacteria, and even insects.
- Lysozyme: It is present in most of the tissue fluids of our body including tears from eyes and saliva. It has the ability to attack and dissolve the cell walls of bacteria.
- Rise in temperature: The rise in temperature of the body or fever in case of any kind of infection is actually a defense mechanism that speeds up all the physiological processes and thus kills the pathogens.
3. Cellular Barriers:
The cellular components of the immune system like WBC or leukocytes, neutrophils and monocytes, lymphocytes mainly natural killer cells (NK Cells) and macrophages phagocytose or engulf the microbes or cellular remains.
A viral-infected cell has a mechanism where they secrete some special class of proteins that can protect the neighbouring cells from being infected by the virus further. These are mainly the interferons. Different classes of cytokines are
- Lymphokine: The cytokines that are secreted from leukocytes and exert their effect on leukocytes are called lymphokines. They are mainly interleukins, e.g. IL- 2, IL-4, IL-12.
- Chemokine: Chemokines are actually small cytokines that are involved in cellular signaling pross, secreted from cells.
- Interferons: The interferons (IFN-5) belong to a large family of cytokines that involved in antiviral defense. For e.g., IFN-8.
- Tumor necrosis factor family: This type of cytokine activates the signaling pathway involved with cell survival, death, and differentiation, constituent and 19 members, process a variety of cellular systems.
- These are haematopoietic cytokines, consisting of various colony-stimulating factors involved in blood cell proliferation and maturation. For e.g., G-CSF, GM-CSF, etc.
It is a low molecular weight dimeric glycoprotein formed in the host cell due to the attack of the virus. This protein prevents further attack of the virus. IFN-a, IFN-b, and IFN-g families of interferons are synthesized by leucocytes, fibroblasts, and lymphocytes respectively.
6. Inflammatory Barrier:
Inflammation causes pain, swelling, and redness. Inflammatory response means the histamine and prostaglandin released by mast cells produce inflammation on the infected area to mobil¬ise the phagocytes to readily attach to the microbes for destroying them.
2. Acquired Immunity
This immunity is formed after birth due to infection of germs naturally or artificially or by the administration of prepared antibody from outside the body. This type of immunity is acquired during one’s lifetime. It can also be termed specific immunity. The following properties have been observed in the case of acquired immunity:
- Specificity: It is the property by virtue of which, the immune system can recognize the foreign particles.
- Diversity: This property helps the immune system to act against a vast range of antigens.
- Discrimination between Self and Non-self: Due to this, the system can recognize and act against foreign substances but avoid acting against any normal components within the body (self).
- Memory: The immune system has the capability to produce specialized cells which get generated on exposure to a specific antigen and are retained in the body so that any further encounter with the same antigen activates a stronger response and eliminates it.
Acquired immunity is of two types – Active acquired immunity and Passive acquired immunity.
A. Active Acquired Immunity
This immunity develops by forming antibodies in the own blood of a person. It may be Natural or Artificial.
- Natural Active Acquired Immunity: This immunity develops by forming antibodies in the blood of a person for a particular disease by natural infection of the germ of that disease in that person, e.g., antibodies formed in the blood of a person after one infection of measles can prevent further infection of measles in that person in future.
- Artificial Active Acquired Immunity: This immunity develops by forming antibodies in the blood of a person for a particular disease by artificial administration of sterile germ or antigen of that disease in that person, e.g., antibodies formed in the blood of a person by pox vaccine prevent the infection of pox in that person in future.
B. Passive Acquired Immunity
This immunity is formed in one’s body by a direct supply of prepared antibodies from other’s blood. It is of two types: Natural and Artificial.
- Natural Passive Acquired Immunity: This immunity is seen in newborn babies by receiving prepared antibodies from the mother’s blood naturally through the placenta or from the mother’s milk, e.g., immunity of newborn babies against measles.
- Artificial Passive Acquired Immunity: This immunity is developed in one’s body by the artificial administration of prepared antibodies from another’s blood, e.g., immunity against tetanus disease by ATS (Anti-Tetanus Serum) injection.
Humoral and Cellular Immunity
T-lymphocyte cells and B-lymphocyte cells are related to acquired immunity.
1. Humoral Immunity
This immunity is formed by B lymphocyte cells of blood against viruses and bacteria.
These lymphocyte cells are formed and mature in the bone marrow and remain in lymph gland, is known as B-lymphocyte cells. It is of two types-
(a) Plasma cell forms antibody immunoglobulin which acts in various ways
- It acts as precipitin to precipitate the antigens.
- It secretes antitoxin which neutralizes the toxin secreted by the antigen.
- It helps the macrophage cells to kill the germs by phagocytosis.
(b) Memory B-cell are those B cells that get activated but remain undifferentiated and do not produce antibodies. They remain dormant for a long time until the body gets exposed to the same antigen again.
2. Cellular Immunity
This immunity is formed by T-lymphocyte cells.
These lymphocyte cells are formed in the bone marrow and mature in the thymus gland known as T-lymphocyte cells. T-lymphocytes are of three types – Helper T-cell, Suppressor T-cell, and Killer T-cell (Cytotoxic T-cell).
- Helper T-cell (CD4 cell): It is of two types T helper 1 (TH1) and T helper 2 (TH2). The antigen after entering the body unites with the receptor of T-cell. As a result, the T-cell is converted to a helper T-cell which secretes lymphokine. Lymphokine stimulates B-lymphocyte to produce antibodies.
- Suppressor T-cell: This cell controls the attack and counterattack of the own cells in animals. That means the cells prevent the reaction of their own antigen and antibody in the same animal, e.g., in AIDS patients, suppressor T-Cell count rises abnormally.
- Killer T-cell: This cell is able to attack directly against germs. In this process, the receptor protein on the surface of the killer T-cell rapidly attacks the germ and destroys it. In addition, the killer T-cell creates a hole in the membrane of the attacked germ cell. Then it secretes toxins in the germ cell and destroys it. The killer T-cell can destroy cancer cells, transplant cells and other cells of the body.
Distinguish between B lymphocyte and T lymphocyte:
|1. Formation and Maturation||It is formed and mature in the bone marrow.||It is formed in the bone marrow and matures in the thymus gland.|
|2. Types||It forms two types of cells – (a) plasma cell and (b) memory cell.||It is of three types – (a) Helper T-cell, (b) Suppressor T-cell, and (c) Killer T-cell.|
|3. Type of Immunity||It forms humoral immunity.||It forms cellular immunity.|
|4. Secreted Substance||It secretes antibodies.||It secretes lymphokine.|
|5. Action Mechanism||It acts by producing antibodies against germs.||It acts directly on germs.|
|6. Action on Other Cells||It cannot act on mutant cancer cells, transplant cells, and other body cells.||It can act on mutant abnormal cancer cell transplant cells and some body cells.|
Distinguish between Helper T-cell (TH) and Killer T-cell (Tc):
|Characters||Helper T-cell||Killer T-cell|
|1. Formation||It is formed by the union of antigen with the receptor of T-cell.||It is not formed by the union of antigen with the receptor of T-cell.|
|2. Secreted Substance||It secretes lymphokines.||It secretes toxin.|
|3. Stimulation||It stimulates B-lymphocyte to form antibody.||It does not stimulate B- lymphocyte to form antibody.|
|4. Action on Other Cells||It destroys macrophage through lymphokine.||It destroys cancer cell, transplant cell, and germs by directly acting on them.|
Distinguish between Humoral and Cell-mediated Immunity:
|Humoral Immunity||Cell-Mediated Immunity|
|1. It constitutes the antibodies that remain present in the blood.||1. It consists of T lymphocytes and B lymphocytes that attack antigens themselves and also produce antibodies.|
|2. It does not attack transplants.||2. It attacks transplants too.|
|3. It can only act against bacteria and viruses.||3. It can act on any kind of pathogen.|
Primary and Secondary Response
Both Humoral and Cell-mediated immunity may act in one of the following two ways:
- Primary Response: When the immune system comes in contact with an antigen for the first time, the response is called primary response. This takes a longer time to develop and is much weaker and lasts for a short time.
- Secondary Response: When the same individual again comes in contact with the same antigen, the immune system responds very rapidly, which is called a secondary response. Such a response is strong and long-lasting, in fact, the person once attacked by measles or smallpox may become immune against any further infections of the same throughout his lifetime.
The hypersensitive response of the immune system of a person after being exposed to any foreign substance is called an allergy. The allergens, i.e., the substances that cause the allergic reaction, maybe dust, spores, pollen, items of personal care, fur, feathers, food, sunlight, etc.
Symptoms of Allergies
Symptoms vary a lot among individuals, but the most common are
- 1. Running eyes and nose
2. Reddened eyes
3. Redness in the skin with itching blisters,
5. Asthma, which affects breathing severely.
Cause of Allergies
Allergens mostly induce the production of antibodies IgE and histamine. This causes dilation of blood vessels and capillaries which leads to leaking of fluid into the tissues. In case of severe reaction, the blood pressure falls so drastically that the patient may become unconscious and even die. This condition is termed as Anaphylactic Shock.
Prevention of Allergies
The use of drugs mainly antihistamine steroids and adrenalin reduces allergic symptoms.
It is a condition where the immunologically active cells or antibodies fail to differentiate between self and non-self cells and attack the normal constituents of the body. The immune system instead of protecting the body, behaves against the body and causes many diseases like rheumatoid arthritis, insulin-dependent diabetes, chronic hepatitis etc. The reason behind such a disorder is still unknown but mostly it is seen that genetic disorders produce such an effect.
Some Autoimmune Diseases of Human Enlisted Here:
|1. Autoimmune Lemolytic Anaemia||RL blood group acts as an antigen.|
|2. Graves’ Disease||Thyroid-stimulating hormone receptors presume to be an antigen.|
|3. Myasthenia Gravis||Acetylcholine receptors presume to be an antigen.|
|4. Rheumatoid Antigen||Synovial joint protein act as antigens.|
|5. Type I Diabetes Mellitus||Antibody attack to pancreatic β-cells.|
- 1. Severe Combined Immuno Deficiency (SCID): Sometimes some newborn children are highly susceptible to various infectious because they lack T-cell and B-cells. Such congenital disease is called SCID.
2. Acquired Immuno Deficiency Syndrome (AIDS):
When there is a reduction of helper T-cells which stilmulates antibody production, cause defence against viral infection is called AIDS.
MHC-I, MHC-II and MHC-III
The major histocompatibility complex (MHC) is a set of cell surface protein hat binds to antigenic part of pathogen and display for T-cells or other immunogenic cells to identify them for destruction. The molecule MHC can be divided into three groups MHC-I, MHC-II and MHC-III. MHC-I is present in all nucleated cells and in platelets MHC-I binds with CD8+ of TC and present antigen, where as MHC-II binds with CD4 of TH and exert its action. The MHC-III is a component of complement system and related with inflammation or heat shock protein (hsp).
In order to develop protection against pathogenic organisms, the component that is used to induce antibody production against the pathogenic organism in the body, is known as vaccine. The British Physician Edward Jenner in 1798 first discovered vaccine for small pox.
Vaccination and Immunization
Vaccination is the process of development of immunization against a specific disease by inoculation of vaccines. Thus vaccines are preparations or suspensions or extracts of dead or attenuated (weakened) pathogens which upon inoculation into a healthy person provides temporary or permanent active or passive immunity by inducing antibody formation.
Some Important Vaccines and Discovery Time:
|Name of Vaccine||Discovery Time|
|1. Small Pox Vaccine||1798|
|2. Rabies Vaccine||1885|
|3. Cholera Vaccine||1892|
|4. Diptheria Toxoid||1923|
|6. Partusis Vaccine||1923|
|7. Tetanus Toxoid||1927|
|8. Influenza Vaccine||1937|
|9. Yellow Fever Vaccine||1937|
|10. Mumps Vaccine||1949|
|11. Salk’s Polio Vaccine||1954|
|12. Sabin Live Oral Polio Vaccine||1957|
|13. Measles Vaccine||1960|
|14. Rubella Vaccine||1962|
|15. Hepatitis A Vaccine||1976|
Some Common Vaccines are
- DPT vaccine for protection against diphtheria, pertussis, and tetanus.
- BCG vaccine is Bacillus of Calmette and Guerin against tuberculosis.
- Oral Polio Vaccine (OPV).
- Typhoid vaccine.
- MMR vaccine against mumps, measles, and rubella.
- TT vaccine against tetanus.
- DT vaccine against diphtheria and tetanus.
Some Diseases and their Natures of Vaccines:
|Disease||Nature of Pathogen||Nature of Vaccine|
|1. Tuberculosis||Bacteria||BCG-energy inactive pathogen|
|2. Thyphoid||Bacteria||Typhoid Vaccine-energy inactive pathogen|
|3. Plague||Bacteria||Plague Vaccine-energy inactive pathogen|
|4. Polio||Virus||Polio vaccine-inactive virus|
|5. Measles||Virus||Measles-inactive virus|
|6. Rubella||Virus||Rubella vaccine-inactive virus|
|7. Mumps||Virus||Mumps Vaccine-inactive virus|
|8. Influenza||Virus||Influenza Vaccine-inactive virus|
|11. Cholera||Bacteria||Cholera vaccine-dead microorganism|
|12. Yellow Fever||Virus||Yellow Vaccine-inactive virus|
|13. Rabies||Virus||Rabbie Vaccine-inactive virus|
|14. Covid-19||Virus||Covaxin, Covishield|
It is a supplementary injection of a vaccine given to maintain the immunization provided by an earlier dose.
Some Vaccines and their Doses:
Type of Vaccines
Vaccines can be classified on the basis of their source. They, therefore, have been classified into 5 types. They are:
- Live Vaccines/Attenuated Vaccines: When live pathogens are weakened or attenuated to make them non-virulent, and are then used as vaccines, such vaccines are termed as Live Vaccines, e.g., Small pox, BCG (Bacillus Calmette Guerin), yellow fever vaccine. Such vaccines can provide immunity through out the life.
- Killed or Inactivated Vaccines: Such vaccines constitute killed pathogens, e.g., Cholera vaccine, Rabies vaccine, Typhoid vaccine.
- Toxoids: Toxins produced by pathogens such as Diphtheria and Tetanus are detoxicated and vaccines are prepared with those. Such vaccines provide passive immunity for a short duration of time, e.g., Diphtheria toxoid, Tetanus toxoid.
- Cellular Fractions: Polysaccharides are the important constituents of cell wall and capsule of different pathogens. These are also competent antigens to induce production of antibodies against them. So they are used for preparation of vaccines, e.g., meningococcal vaccine, pneumococcal vaccine.
- Combinations: If a vaccine is prepared by mixing all the above mentioned components, they are called combination vaccines, e.g., DPT, MMR.