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Home , Active immunization, Antiserum, Passive immunity

The system of the body which protects it from various infectious is known as . The study of this system is known as immunology. Active : After birth, gradually the infants start synthesizing their own and acquire active immunity. : When the maternal , IgG passes through the into the foetus, it develops passive immunity in the infants against for the first six months.

Active acquired immunity: The weathering germs or dead ; () are injected into a normal person to develop immunity by producing antibodies is called . These pathogens given in a , are unable to cause the disease, but are sufficient to stimulate the formation of antibodies by the cells of the host. This is known as active acquired immunity. The solution of weakened antigens (pathogens) that are injected into the body is called as . The disease like small pox, , typhoid, cholera and plague are treated by active acquired immunity.

Passive acquired immunity: Sometimes persons do not produce antibodies for some antigens (pathogens). Another animal commonly a horse is injected with the which produce antibodies. These antibodies are isolated and are then injected into the . This is known as passive acquired immunity. By this process, diseases like , scarlet and are treated. Acquired immunity: In this article we will discuss about the active and passive type of acquired immunity. Adaptive immunity that is induced by natural exposure to a pathogen or by vaccination. It can be categorized into two types:

Type # 1. Active Immunity:

Naturally acquired active immunity: Active immunity is acquired through continuing, subclinical infections, caused by and , which largely remain unnoticed and which is more advantageous than passive immunity. Artificially acquired active immunity: This type of immunity is usually obtained through vaccination or through administration of . Vaccines are killed or live attenuated microorganisms, whereas the toxoids are prepa rations of , which have been inactivated by certain clinical treatments or modifications so as to make them non-toxic in nature. Type # 2. Passive Immunity: Adaptive immunity is conferred by the transfer of immune products, such as antibody or sensitized T-cells, from an immune individual to non immune one. It is of two types: Naturally acquired passive immunity: This can be acquired through trans-placental transfer of immunoglobulins (IgG) from mother to the foetus. This immunity lasts for about six months after birth. These antibodies of maternal origin protect the foetus and the infant from diptheria, streptococci, tetanus, rubella, mumps, and polio through passive immunity. The secretory immunoglobulin (IgA) present in the mother’s provides local immunity in the gastrointestinal tract of the sucking infants. More over human colostrums are rich in and (T-cells) which can survive in the intestine of the suckling infant for sometime, and thus can transfer cell mediated immunity. Artificially acquired passive immunity: It is achieved by administering specific anti bodies or from one individual to another unimmunized individual, for a particular antigen. Routine passive is done against different diseases like tetanus, botulinum, diptheria, hepatitis, and . Antibodies against a microbe or its antigen or can be raised in a suitable animal through repeated injection of suitable antigen. Immunization Immunization is the process of rendering a subject immune, or of becoming immune, called also and vaccination. Immunization: is the means of providing specific protection against most common and damaging pathogens. Immunization, orimmunisation, is the process by which an individual's immune system becomes fortified against an agent (known as the ). Passive immunization is neither spontaneous on the part of the patient, nor, active response by the patient, the stimulus having been applied externally. Treatment that provides immunity through the transfer of antibodies obtained from an immune individual.

Immunization, or immunisation, is the process by which an individual's immune system becomes fortified against an agent (known as the immunogen). When this system is exposed to molecules that are foreign to the body, called non-self, it will orchestrate an , and it will also develop the ability to quickly respond to a subsequent encounter because of immunological memory. This is a function of the . Therefore, by exposing an animal to an immunogen in a controlled way, its body can learn to protect itself: this is called . The most important elements of the immune system that are improved by immunization are the T cells, B cells, and the antibodies B cells produce. Memory B cells and memory T cells are responsible for a swift response to a second encounter with a foreign molecule. Passive immunization is direct introduction of these elements into the body, instead of production of these elements by the body itself. Immunization is done through various techniques, most commonly vaccination. Vaccines against microorganisms that cause diseases can prepare the body's immune system, thus helping to fight or prevent an . The fact that mutations can cause cells to produce proteins or other molecules that are known to the body forms the theoretical basis for therapeutic cancer vaccines. Other molecules can be used for immunization as well, for example in experimental vaccines against nicotine (NicVAX) or the hormone ghrelin in experiments to create an obesity vaccine. are often widely stated as less risky and an easier way to become immune to a particular disease than risking a milder form of the disease itself. They are important for both adults and children in that they can protect us from the many diseases out there. Immunization not only protects children against deadly diseases but also helps in developing children's immune systems. Through the use of immunizations, some infections and diseases have almost completely been eradicated throughout the United States and the World. One example is polio. Thanks to dedicated health care professionals and the parents of children who vaccinated on schedule, polio has been eliminated in the U.S. since 1979. Polio is still found in other parts of the world so certain people could still be at risk of getting it. This includes those people who have never had the vaccine, those who didn't receive all doses of the vaccine, or those traveling to areas of the world where polio is still prevalent. Active immunization/vaccination has been named one of the "Ten Great Public Health Achievements in the 20th Century". History Before the introduction of vaccines, people could only become immune to an infectious disease by contracting the disease and surviving it. (variola) was prevented in this way by inoculation, which produced a milder effect than the natural disease. The first clear reference to smallpox inoculation was made by the Chinese author Wan Quan (1499–1582) in his Douzhen xinfa (痘疹心法) published in 1549.[2] In China, powdered smallpox scabs were blown up the noses of the healthy. The patients would then develop a mild case of the disease and from then on were immune to it. The technique did have a 0.5–2.0% mortality rate, but that was considerably less than the 20– 30% mortality rate of the disease itself. Two reports on the Chinese practice of inoculation were received by the Royal Society in London in 1700; one by Dr. Martin Lister who received a report by an employee of the East India Company stationed in China and another by Clopton Havers.[3] According to Voltaire (1742), the Turks derived their use of inoculation from neighbouring Circassia. Voltaire does not speculate on where the Circassians derived their technique from, though he reports that the Chinese have practiced it "these hundred years". It was introduced into England from Turkey by Lady Mary Wortley Montagu in 1721 and used by Zabdiel Boylston in Boston the same year. In 1798 introduced inoculation with cowpox (), a much safer procedure. This procedure, referred to as vaccination, gradually replaced smallpox inoculation, now called variolation to distinguish it from vaccination. Until the 1880s vaccine/vaccination referred only to smallpox, but developed immunization methods for chicken cholera and in and for human rabies, and suggested that the terms vaccine/vaccination should be extended to cover the new procedures. This can cause confusion if care is not taken to specify which vaccine is used e.g. or vaccine. Passive and active immunization Immunization can be achieved in an active or passive manner: vaccination is an active form of immunization. Active immunization Active immunization can occur naturally when a person comes in contact with, for example, a microbe. The immune system will eventually create antibodies and other defenses against the microbe. The next time, the immune response against this microbe can be very efficient; this is the case in many of the childhood infections that a person only contracts once, but then is immune. Artificial active immunization is where the microbe, or parts of it, are injected into the person before they are able to take it in naturally. If whole microbes are used, they are pre- treated. The importance of immunization is so great that the American Centers for Disease Control and Prevention has named it one of the "Ten Great Public Health Achievements in the 20th Century".[5] Live attenuated vaccines have decreased pathogenicity. Their effectiveness depends on the immune systems ability to replicate and elicits a response similar to natural infection. It is usually effective with a single dose. Examples of live, attenuated vaccines include measles, mumps, rubella, MMR, , varicella, rotavirus, and influenza (LAIV). Passive immunization Passive immunization is where pre-synthesized elements of the immune system are transferred to a person so that the body does not need to produce these elements itself. Currently, antibodies can be used for passive immunization. This method of immunization begins to work very quickly, but it is short lasting, because the antibodies are naturally broken down, and if there are no B cells to produce more antibodies, they will disappear. Passive immunization occurs physiologically, when antibodies are transferred from mother to fetus during pregnancy, to protect the fetus before and shortly after birth. Artificial passive immunization is normally administered by injection and is used if there has been a recent outbreak of a particular disease or as an emergency treatment for toxicity, as in for tetanus. The antibodies can be produced in animals, called " ," although there is a high chance of anaphylactic because of immunity against animal serum itself. Thus, humanized antibodies produced in vitro by cell culture are used instead if available.

Passive immunity Passive immunity is protection provided from the transfer of antibodies from immune individuals, most commonly across the placenta or less often from the transfusion of blood or blood products including immunoglobulin. Protection provided by the cross-placental transfer of antibodies from mother to child is more effective against some infections (e.g. tetanus and measles) than for others (e.g. polio and ). This protection is temporary – commonly for only a few weeks or months. How vaccines work Vaccines produce their protective effect by inducing active immunity and providing immunological memory. Immunological memory enables the immune system to recognise and respond rapidly to exposure to natural infection at a later date and thus to prevent or modify the disease. Antibodies can be detected in blood or serum, but, even in the absence of detectable antibodies, immunological memory may still be present. Cell-mediated responses to some vaccines (e.g. BCG, see Chapter 32) may be detectable by skin testing but do not necessarily indicate protection. Vaccines can be made from inactivated (killed) or attenuated live organisms, secreted products, recombinant components or the constituents of cell walls. Vaccines such as pertussis and inactivated poliomyelitis virus (IPV) contain inactivated bacteria or viruses. Other vaccines contain only the antigens that are important for protection. For example, tetanus and diphtheria vaccines contain inactivated toxins (toxoids), contains a surface called haemagglutinin, and contains the polysaccharide from the capsule. Live attenuated vaccines include yellow fever; measles, mumps and rubella (MMR); andBCG. From birth and in early infancy and childhood, are exposed to countless numbers of foreign antigens and infectious agents in the everyday environment. Responding to these stimuli helps the immune system to develop and mature. Compared with exposure in the natural environment, vaccines provide specific stimulation to a small number of antigens. Responding to these specific antigens uses only a tiny proportion of the capacity of an infant’s immune system (Offit et al., 2002). If an infant’s immune system could be exhausted by multiple vaccines, one would expect vaccinated children to be at a higher risk of serious infections. Studies to investigate whether vaccines increase susceptibility to serious infections have shown no evidence of such an effect, with infection rates generally being lower in vaccinated children (Hviid et al., 2005, Miller et al., 2003).

Inactivated vaccines A first injection of an or in an individual without prior exposure to the antigen produces a primary antibody response. This response is dominated by IgM antibody initially, followed by IgG antibody. Two or more injections may be needed to elicit such a response in young infants. This is usually called the primary course. Depending on the potency of the product and the time interval, further injections will lead to an accelerated response dominated by IgG – the secondary response. Following a primary course of vaccination, antibodies may persist for months or years. Even if the level of detectable antibody subsequently falls, the immune system has been primed and an individual may be protected. Further reinforcing doses of vaccine are used to boost immunity and to provide longer-term protection.

Inactivated vaccines cannot cause the disease that they are designed to prevent. Plain polysaccharide antigens do not stimulate the immune system as broadly as protein antigens such as tetanus, diphtheria or influenza. Therefore, protection from such vaccines is not long-lasting and response in infants and young children is poor. Some polysaccharide vaccines have been enhanced by conjugation – where the polysaccharide antigen is attached to a protein carrier (e.g. Hib and MenC vaccines). This enables the immune system to respond more broadly to the antigen to provide immunological memory, even in young children. Some inactivated vaccines contain adjuvants, substances that enhance the antibody response. Most combination vaccines contain adjuvants such as aluminium phosphate or aluminium hydroxide. Live vaccines Live attenuated virus vaccines, such as MMR, usually promote a full, longlasting antibody response after one or two doses. To produce an immune response, the live organism must replicate (grow) in the vaccinated individual over a period of time (days or weeks). The immune system responds in the same way as it does to natural infection. It usually does this without causing the disease itself (because the vaccine virus is weakened or ‘attenuated’) but, for some vaccines, a mild form of the disease may rarely occur (e.g. a rash following measles-containing vaccines).

Types of Vaccines There are several basic types of vaccines. Some vaccines are described here. 1. Attenuated whole-agent vaccines use living but attenuated (weakened) microbes. Examples of attenuated vaccines are the Sabin and those used against measles, mumps and rubella (MMR). The widely used vaccine against the bacillus and certain of the newly introduced, orally administered typhoid vaccines contain attenuated bacteria. 2. Inactivated whole-agent vaccines use microbes that have been killed. Inactivated virus vaccines used in humans include those against rabies, influenza and polio (the Salk polio vaccine). Inactivated bacterial vaccines include those for pneumococcal pneumonia, cholera, pertussis (whooping cough) and typhoid. 3. Toxoids which are inactivated toxins, are vaccines directed at the toxins produced by a pathogen. Examples. Vaccines against tetanus and diphtheria. 4. Subunit vaccines use only those antigenic fragments of a microorganism that best stimulate an immune response. Subunit vaccines that are produced by genetic modification techniques, meaning that other microbes are programmed to produce the desired antigenic fraction, are called recombinant vaccines. For example, the vaccine against the hepatitis В virus consists of a portion of the viral protein coat that is produced by genetically modified yeast. 5. Conjugated vaccines have been developed in recent years to deal with the poor immune response of children. The polysaccharides are combined with porteins such as diphtheria toxoid. This approach has led to the very successful vaccine for Haemophilic influenza type b, which gives significant protection. 6. Nucleic acid vaccines or DNA vaccines are among the newest and most promising vaccines, although they have not yet resulted in any commercial vaccine for humans. Experiments with animals show that plasmids of “naked” DNA injected into muscle results in the production of the protein encoded in the DNA. These proteins stimulate an immune response. A problem with this type of vaccine is that the DNA remains effective only until it is degraded. Indications are that RNA, which could replicate in the recipient, might be a more effective agent. Vaccines are also classified as follows. 1. First generation vaccines: These are produced by conventional methods, e.g., small pox vaccine, Salk’s polio vaccine. 2. Second generation vaccines:These are prepared with the help of genetic engineering technique, e.g., vaccines against Hepatitis В and Herpes virus. 3. Third generation vaccines: These are synthetic vaccines which are under trial. Vaccines under study: Vaccines against Malaria, Leprosy, Herpes, Hepatitis C, AIDS, Dental caries, etc. are under study. Immunisation and Pregnancy: The question of whether immunisation of a pregnant woman presents any danger for the foetus is frequently raised. Ideally, immunisation should be performed before gestation, since some vaccines are not perfectly safe during pregnancy. Pregnant women are however, often vaccinated either because they travel to foreign coun tries or when an epidemic occurs. Vaccines which are safe during pregnancy are tetanus, influenza, inactivated poliomyeli tis, cholera and .