Vaccines contain the same antigens that are found on pathogens that cause the associated disease, but exposure to the antigens in vaccines is controlled. By priming Priming The process of artificial induction of immunity, in order to protect against infectious disease. Priming the immune system involves sensitizing or stimulating an immune response with an antigen that can produce immunity to a disease-causing organism or toxin poison.
As with B-cells, activated T-cells also undergo clonal expansion which produces additional effector T-cells for the current infection and memory T-cells for future infections with this antigen. Immunization can be derived from either passive or active means. These means can be from either natural or artificial sources. Natural sources are due to exposure to the environment, humans, and animals.
In contrast, artificial sources are due to medical interventions. Passive immunization occurs with the transfer to preformed antibodies to an unimmunized individual. This individual would then develop a temporary immunity to a particular organism or toxin due to the presence of these preformed antibodies.
Once these preformed antibodies have been destroyed, the individual would no longer have immunity to this microorganism or toxin. Passive immunization can occur either naturally or artificially. Excellent examples of natural passive immunization are the passage of maternal antibodies through the placenta to the fetus and the passage of these maternal antibodies to the infant through the colostrum and milk. Excellent examples of artificial passive immunization include the administration of pooled human immune gamma globulin and antivenin.
These gamma globulins and antivenins provide temporary immunity to either a particular illness or venom. Concurrent with these effects of this temporary immunity from the preformed antibodies, the individual's own body is likely to be in the early stages of developing its own active immune response.
Active immunization occurs with the exposure of an unimmunized individual to a pathogenic agent. The immune system of this individual then begins the process of developing immunity to this agent. In contrast to passive immunization, active immunization typically produces long-term immunity due to the stimulation of the individual's immune system.
The process of stimulating the immune system against a pathogenic agent will be further discussed in this article. Active immunization can occur either naturally or artificially. An excellent example of natural active immunization is exposure to influenza. The body then begins the process of developing long-term immunity to the influenza virus. Excellent examples of artificial active immunization include the different types of immunizations that will be discussed in this article.
These immunizations mimic the stimulation necessary for immune development yet do not produce active disease. As with any challenge to the immune system, the body must first detect the threat whether it is a pathogenic agent or an immunization. This initial detection typically is done by the innate immune system; although, B-cells may also perform this function. This detection process begins when the immune system recognizes epitopes on antigens.
Epitopes are small subregions on the antigens that simulate immune recognition. Multiple components of the innate immune system will then respond to this challenge. These components of innate immunity will opsonize or bind to the agent and aid in its engulfment by antigen-presenting cells such as macrophages or monocytes.
These antigen-presenting cell s will then process the antigens from this pathogenic agent and insert the processed antigen along with the MHC protein onto the surface on the antigen-presenting cell. If it is a viral antigen, the antigen will be bound with MHC I protein and presented by the antigen-presenting cell to a CD8 cell which will likely trigger cell-mediated immunity. If it is a bacterial or parasitic antigen, the antigen will be bound with MHC II protein and presented by the antigen-presenting cell to a CD4 cell which will likely trigger antibody-mediated immunity.
There are a variety of vaccine types that are either currently in use or in development for the prevention of infectious diseases.
Under ideal conditions, vaccines should trigger the innate immune system and both arms of the adaptive immune system. First, live, attenuated vaccines as exemplified by the vaccines against measles, mumps, and chickenpox contain laboratory-weakened versions of the original pathogenic agent.
Therefore, these vaccines produce a strong cellular and antibody responses and typically produce long-term immunity with only one to two doses of vaccine. Typically, it is less difficult to create live, attenuated vaccines with viruses rather than bacteria because viruses have fewer genes so it is easier to control the viral characteristics. However, because these vaccines contain living microorganisms, refrigeration is required to preserve potency; and, there is the possibility of reversion to the original virulent form of the pathogenic agent.
In addition, live vaccines cannot be given to individuals with weakened immune systems because the vaccine produces actual disease. Inactivated vaccines as exemplified by the inactivated influenza vaccine are produced by destroying a pathogenic agent with chemicals, heat, or radiation. This inactivation of the microorganism makes the vaccine more stable. These vaccines do not require refrigeration and can be freeze-dried for transport.
However, these vaccines produce weaker immune responses therefore additional booster shots are required to maintain immunity. In experiments with mice by Raz et al. The irradiated vaccine also stimulated a protective response from T-cells which previously had only been shown to occur with vaccines made from live, weakened Listeria bacteria.
Subunit vaccines as exemplified by the recombinant hepatitis B vaccine include only epitopes specific parts of antigens to which antibodies or T-cells recognize and bind that most readily stimulate the immune system.
Because these vaccines only use a few specific antigens, this reduces the likelihood of adverse reactions; however, this specificity increases the difficulty of determining which antigens should be included in the vaccine. Toxoid vaccines as exemplified by the diphtheria and tetanus vaccines are produced by inactivating bacterial toxins with formalin. These toxoids stimulate an immune response against the bacterial toxins. Conjugate vaccines as exemplified by the Haemophilus influenzae type B Hib vaccine are a special type of subunit vaccine.
In a conjugate vaccine, antigens or toxoids from a microbe are linked to polysaccharides from the outer coating of that microbe to stimulate immunity especially in infants. Depending on the type of infectious organism, the response required to remove it varies. The body prevents infection through a number of non-specific and specific mechanisms working on their own or together.
The largest of all is the skin which acts as a strong, waterproof, physical barrier and very few organisms are able to penetrate undamaged skin. There are other physical barriers and a variety of chemical defences. Examples of these non-specific defences are given below:. An immune response is triggered when the immune system is alerted that something foreign has entered the body.
Triggers include the release of chemicals by damaged cells and inflammation, and changes in blood supply to an area of damage which attract white blood cells. White blood cells destroy the infection or convey chemical messages to other parts of the immune system. As blood and tissue fluids circulate around the body, various components of the immune system are continually surveying for potential sources of attack or abnormal cells.
Antigens are usually either proteins or polysaccharides long chains of sugar molecules that make up the cell wall of certain bacteria. Viruses can contain as few as three antigens to more than as for herpes and pox viruses; whereas protozoa, fungi and bacteria are larger, more complex organisms and contain hundreds to thousands of antigens.
An immune response initially involves the production of antibodies that can bind to a particular antigen and the activation of antigen-specific white blood cells. Antibodies immunoglobulins; Ig are protein molecules that bind specifically to a particular part of an antigen, so called antigenic site or epitope.
They are found in the blood and tissue fluids, including mucus secretions, saliva and breast milk. Normally, low levels of antibodies circulate in the body tissue fluids. However, when an immune response is activated greater quantities are produced to specifically target the foreign material.
Vaccination increases the levels of circulating antibodies against a certain antigen. Antibodies are produced by a type of white blood cell lymphocyte called B cells. Each B cell can only produce antibodies against one specific epitope.
This is an example of:. A patient gets a cold, and recovers a few days later. Skip to main content. Adaptive Specific Host Defenses. Search for:. Vaccines Learning Objectives Compare the various kinds of artificial immunity Differentiate between variolation and vaccination Describe different types of vaccines and explain their respective advantages and disadvantages.
Think about It What is the difference between active and passive immunity? What kind of immunity is conferred by a vaccine? Vaccination: Obligation or Choice A growing number of parents are choosing not to vaccinate their children. Think about It What is the difference between variolation and vaccination for smallpox? Explain why vaccination is less risky than variolation. Think about It What is the risk associated with a live attenuated vaccine?
In countries with developed public health systems, many vaccines are routinely administered to children and adults. Vaccine schedules are changed periodically, based on new information and research results gathered by public health agencies.
Key Concepts and Summary Adaptive immunity can be divided into four distinct classifications: natural active immunity, natural passive immunity, artificial passive immunity, and artificial active immunity. Artificial active immunity is the foundation for vaccination and vaccine development. Vaccination programs not only confer artificial immunity on individuals, but also foster herd immunity in populations.
Variolation against smallpox originated in the tenth century in China, but the procedure was risky because it could cause the disease it was intended to prevent. Modern vaccination was developed by Edward Jenner, who developed the practice of inoculating patients with infectious materials from cowpox lesions to prevent smallpox. Live attenuated vaccines and inactivated vaccines contain whole pathogens that are weak, killed, or inactivated.
Subunit vaccines, toxoid vaccines, and conjugate vaccines contain acellular components with antigens that stimulate an immune response. Multiple Choice A patient is bitten by a dog with confirmed rabies infection.
This is an example of: Natural active immunity Artificial active immunity Natural passive immunity Artificial passive immunity Show Answer Answer d. This is an example of artificial passive immunity.
Show Answer Answer a. This is an example of natural active immunity. Matching Match each type of vaccine with the corresponding example. Weakened influenza virions that can only replicate in the slightly lower temperatures of the nasal passages are sprayed into the nose. They do not cause serious flu symptoms, but still produce an active infection that induces a protective adaptive immune response.
Tetanus toxin molecules are harvested and chemically treated to render them harmless. Influenza virus particles grown in chicken eggs are harvested and chemically treated to render them noninfectious.
These immunogenic particles are then purified and packaged and administered as an injection. The gene for hepatitis B virus surface antigen is inserted into a yeast genome. The modified yeast is grown and the virus protein is produced, harvested, purified, and used in a vaccine. Show Answer An attenuated pathogen is in a weakened state; it is still capable of stimulating an immune response but does not cause a disease. Show Answer Artificial passive immunity occurs when antibodies from one individual are harvested and given to another to protect against disease or treat active disease.
Show Answer In the practice of variolation , scabs from smallpox victims were used to immunize susceptible individuals against smallpox.
Think about It Briefly compare the pros and cons of inactivated versus live attenuated vaccines. Mupapa, M. Massamba, K.
0コメント