A vaccine is a biological preparation that improves immunity to a particular disease. A vaccine typically contains an agent that resembles a disease-causing microorganism, and is often made from weakened or killed forms of the microbe, its toxins or one of its surface proteins. The agent stimulates the body’s immune system to recognize the agent as foreign, destroy it, and “remember” it, so that the immune system can more easily recognize and destroy any of these Microorganisms that it later encounters.
Introduction to immunity
The immune system refers to a collection of cells and proteins that function to protect the skin, respiratory passages, intestinal tract and other areas from foreign antigens, such as microbes (organisms such as bacteria, Fungi, and parasites), viruses, cancer cells, and toxins. The immune system can be simplistically viewed as having two “lines of defense”: innate immunity and adaptive immunity. Innate immunity represents the first line of defense to an intruding pathogen. It is an antigen-independent (non-specific) defense mechanism that is used by the host immediately or within hours of encountering an antigen. The innate immune response has no immunologic memory and, therefore, it is unable to recognize or “memorize” the same pathogen should the body be exposed to it in the future. Adaptive immunity, on the other hand, is antigen-dependent and antigen-specific and, therefore, involves a lag time between exposure to the antigen and maximal response. The hallmark of adaptive immunity is the capacity for memory which enables the host to mount a more rapid and efficient immune response upon subsequent exposure to the antigen. Innate and adaptive immunity are not mutually exclusive mechanisms of host defense, but rather are complementary, with defects in either system resulting in host vulnerability.
Innate immunity
The primary function of innate immunity is the recruitment of immune cells to sites of infection and inflammation through the production of cytokines (small proteins involved in cell-cell Communication). Cytokine production leads to the release of antibodies and other proteins and glycoproteins which activate the complement system, a biochemical cascade that functions to identify and opsonize (coat) foreign antigens, rendering them susceptible to phagocytosis (process by which cells engulf microbes and remove cell debris). The innate immune response also promotes clearance of dead cells or antibody complexes and removes foreign substances present in organs, Tissues, blood and lymph. It can also activate the adaptive immune response through a process known as antigen presentation.
Numerous cells are involved in the innate immune response such as phagocytes (macrophages and neutrophils), dendritic cells, mast cells, basophils, eosinophils, natural killer (NK) cells and lymphocytes (T cells). Phagocytes are sub-divided into two main cell types: neutrophils and macrophages. Both of these cells share a similar function: to engulf (phagocytose) microbes. In addition to their phagocytic properties, neutrophils contain granules that, when released, assist in the elimination of pathogenic microbes. Unlike neutrophils (which are short-lived cells), macrophages are long-lived cells that not only play a role in phagocytosis, but are also involved in antigen presentation to T cells. Macrophages are named according to the tissue in which they reside. For example, macrophages present in the liver are called Kupffer cells while those present in the connective tissue are termed histiocytes.
Adaptive immunity
Adaptive immunity develops when innate immunity is ineffective in eliminating infectious agents and the infection is established. The primary functions of the adaptive immune response are the recognition of specific “non-self” antigens in the presence of “self” antigens; the generation of pathogen-specific immunologic effector pathways that eliminate specific pathogens or pathogen-infected cells; and the development of an immunologic memory that can quickly eliminate a specific pathogen should subsequent infections occur. The cells of the adaptive immune system include: T cells, which are activated through the action of antigen presenting cells (APCs), and B cells.
T cells derive from hematopoietic stem cells in bone marrow and, following Migration, mature in the thymus. These cells express a unique antigen-binding receptor on their membrane, known as the T-cell receptor (TCR), and as previously mentioned, require the action of APCs (usually dendritic cells, but also macrophages, B cells, fibroblasts and epithelial cells) to recognize a specific antigen.
The surfaces of APCs express cell-surface proteins known as the major histocompatibility complex (MHC). MHC are classified as either class I (also termed human leukocyte antigen [HLA] A, B and C) which are found on all nucleated cells, or class II (also termed HLA, DP, DQ and DR) which are found on only certain cells of the immune system, including macrophages, dendritic cells and B cells. Class I MHC Molecules present endogenous (intracellular) peptides while class II molecules present exogenous (extracellular) peptides. The MHC protein displays fragments of antigens (peptides) when a cell is infected with a pathogen or has phagocytosed foreign proteins.
T cells are activated when they encounter an APC that has digested an antigen and is displaying antigen fragments bound to its MHC molecules. The MHC-antigen complex activates the TCR and the T cell secretes cytokines which further control the immune response. This antigen presentation process stimulates T cells to differentiate into either cytotoxic T cells (CD8+ cells) or T-helper (Th) cells (CD4+ cells). Cytotoxic T cells are primarily involved in the destruction of cells infected by foreign agents. They are activated by the interaction of their TCR with peptide-bound MHC class I molecules. Clonal expansion of cytotoxic T cells produce effector cells which release perforin and granzyme (proteins that causes lysis of target cells) and granulysin (a substance that induces apoptosis of target cells). Upon resolution of the infection, most effector cells die and are cleared by phagocytes. However, a few of these cells are retained as memory cells that can quickly differentiate into effector cells upon subsequent encounters with the same antigen.
T helper (Th) cells play an important role in establishing and maximizing the immune response. These cells have no cytotoxic or phagocytic activity, and cannot kill infected cells or clear pathogens. However, they “mediate” the immune response by directing other cells to perform these tasks. Th cells are activated through TCR recognition of antigen bound to class II MHC molecules. Once activated, Th cells release cytokines that influence the activity of many cell types, including the APCs that activate them.
Passive Immunity
Passive immunity is the transfer of antibody produced by one human or other animal to another. Passive immunity provides protection against some infections, but this protec – tion is temporary. The antibodies will degrade during a period of weeks to months, and the recipient will no longer be protected. The most common form of passive immunity is that which an infant receives from its mother. Antibodies are trans – ported across the placenta during the last 1–2 months of pregnancy. As a result, a full-term infant will have the same antibodies as its mother. These antibodies will protect the infant from certain diseases for up to a year.
Protection is better against some diseases (e.g., measles, rubella, tetanus) than others (e.g., polio, pertussis). Many types of blood products contain antibody. Some products (e.g., washed or reconstituted red blood cells) contain a relatively small amount of antibody, and some (e.g., intravenous immune globulin and plasma products) contain a large amount.
In addition to blood products used for transfusion (e.g., whole blood, red cells, and platelets) there are three major sources of antibody used in human medicine. These are homologous pooled human antibody, homologous human hyperimmune globulin, and heterologous hyperimmune serum.
Homologous pooled human antibody is also known as immune globulin. It is produced by combining (pooling) the IgG antibody fraction from thousands of adult donors in the United States. Because it comes from many different donors, it contains antibody to many different antigens. It is used primarily for postexposure prophylaxis for hepatitis A and measles and treatment of certain congenital immuno – globulin deficiencies.
Active Immunity
Active immunity is stimulation of the immune system to produce antigen-specific humoral (antibody) and cellular immunity. Unlike passive immunity, which is temporary, active immunity usually lasts for many years, often for a lifetime.
One way to acquire active immunity is to survive infection with the disease-causing form of the organism. In general, once persons recover from infectious diseases, they will have lifelong immunity to that disease. The persistence of protection for many years after the infection is known as immunologic memory. Following exposure of the immune system to an antigen, certain cells (memory B cells) continue to circulate in the blood (and also reside in the bone marrow) for many years. Upon reexposure to the antigen, these memory cells begin to replicate and produce antibody very rapidly to reestablish protection.
Another way to produce active immunity is by vaccination. Vaccines interact with the immune system and often produce an immune response similar to that produced by the natural infection, but they do not subject the recipient to the disease and its potential complications. Many vaccines also produce immunologic memory similar to that acquired by having the natural disease.,
Introduction to immunity
Immunity is the body’s ability to protect itself from harmful substances and germs, such as bacteria, viruses, and parasites. There are two main types of immunity: innate immunity and adaptive immunity.
Innate immunity is the body’s first line of defense against infection. It is present at birth and does not change over time. Innate immunity includes physical barriers, such as the skin and mucous membranes, as well as chemical defenses, such as white blood cells and antibodies.
Adaptive immunity is the body’s second line of defense against infection. It develops after exposure to a particular germ and becomes stronger each time the body is exposed to that germ. Adaptive immunity includes B cells and T cells, which are white blood cells that produce antibodies and help to destroy infected cells.
Innate immunity and adaptive immunity work together to protect the body from infection. Innate immunity provides a quick response to infection, while adaptive immunity provides a more specific and long-lasting response.
Innate immunity
Innate immunity is the body’s first line of defense against infection. It is present at birth and does not change over time. Innate immunity includes physical barriers, such as the skin and mucous membranes, as well as chemical defenses, such as white blood cells and antibodies.
The skin is the body’s largest organ and provides a physical barrier against infection. The skin is covered in a layer of dead cells that help to trap germs. The skin also produces sweat and sebum, which contain chemicals that can kill germs.
The mucous membranes line the inside of the body, such as the nose, mouth, throat, and lungs. The mucous membranes produce mucus, which traps germs and helps to flush them out of the body. The mucous membranes also contain ENZYMES that can kill germs.
White blood cells are a type of blood cell that helps to fight infection. White blood cells can engulf and destroy germs, or they can produce antibodies that attack germs.
Antibodies are proteins that are produced by white blood cells. Antibodies bind to specific germs and help to destroy them.
Adaptive immunity
Adaptive immunity is the body’s second line of defense against infection. It develops after exposure to a particular germ and becomes stronger each time the body is exposed to that germ. Adaptive immunity includes B cells and T cells, which are white blood cells that produce antibodies and help to destroy infected cells.
B cells are a type of white blood cell that produces antibodies. Antibodies are proteins that bind to specific germs and help to destroy them. When a B cell is exposed to a germ for the first time, it produces antibodies that are specific to that germ. These antibodies then circulate in the blood and help to protect the body from future infection with that germ.
T cells are a type of white blood cell that helps to destroy infected cells. T cells can kill infected cells directly, or they can help to activate other white blood cells to kill infected cells.
Vaccines
A vaccine is a preparation that is used to stimulate the body’s immune system to produce antibodies against a particular disease. Vaccines are made from weakened or killed forms of the disease-causing organism, or from a part of the organism. When a person is vaccinated, their immune system produces antibodies against the disease-causing organism. These antibodies protect the person from getting sick if they are exposed to the disease in the future.
Vaccines are one of the most important tools for preventing disease. They have helped to eradicate diseases such as smallpox and polio, and they have made other diseases, such as measles and mumps, much less common. Vaccines are safe and effective, and they are an important part of keeping people healthy.
How vaccines work
Vaccines work by stimulating the body’s immune system to produce antibodies against a particular disease. When a person is vaccinated, their immune system produces antibodies against the disease-causing organism. These antibodies protect the person from getting sick if they are exposed to the disease in the future.
Vaccines work by mimicking an infection. When a person is vaccinated, their immune system responds as if they have been infected with the disease. This response causes the body to produce antibodies against the disease-causing organism. These antibodies then circulate in the blood and help to protect the person from future infection.
Types of vaccines
There are many different types of vaccines. Some vaccines are made from weakened or killed forms of the disease-causing organism. Other vaccines are made from a part of the disease-causing organism, such as a protein or a piece of DNA. Some vaccines are given as a single shot, while others are given in a series of shots.
Vaccines are available for a wide variety of diseases, including measles, mumps, rubella, polio, tetanus, diphtheria, pertussis, hepatitis B, chickenpox, pneumonia, rotavirus, and influenza.
What is immunity?
Immunity is the body’s ability to protect itself from harmful substances and germs.
What are the different types of immunity?
There are two types of immunity: innate immunity and acquired immunity. Innate immunity is the body’s natural defense system that is present at birth. Acquired immunity is the body’s ability to develop resistance to a specific disease after being exposed to it.
How does the body develop immunity?
The body develops immunity through a process called vaccination. Vaccination is the process of exposing the body to a weakened or inactivated form of a disease-causing organism in order to stimulate the body’s immune system to produce antibodies that will protect against the disease.
What are the benefits of vaccination?
Vaccination is one of the most effective ways to prevent disease. Vaccines have helped to eradicate diseases such as smallpox and polio, and they have significantly reduced the incidence of other diseases such as measles, mumps, and rubella.
What are the risks of vaccination?
Vaccines are very safe, but there is a small risk of side effects. The most common side effects of vaccination are mild and go away on their own within a few days. Serious side effects are rare.
Who should get vaccinated?
Everyone should get vaccinated, but some people are at higher risk for certain diseases and should talk to their doctor about whether they need additional vaccines. These people include:
- People who have a weakened immune system
- People who are pregnant
- People who travel to areas where certain diseases are common
Where can I get vaccinated?
Vaccines are available at most doctor’s offices, clinics, and pharmacies. You can also find information about vaccination clinics in your area by contacting your local Health department.
What should I do if I have questions about vaccination?
If you have any questions about vaccination, talk to your doctor. You can also find information about vaccination on the websites of the Centers for Disease Control and Prevention (CDC) and the World Health Organization (WHO).
Which of the following is not a type of immunity?
(A) Innate immunity
(B) Adaptive immunity
(C) Passive immunity
(D) Active immunityWhich of the following is an example of innate immunity?
(A) The production of antibodies
(B) The activation of T cells
(C) The production of interferon
(D) The inflammation responseWhich of the following is an example of adaptive immunity?
(A) The production of antibodies
(B) The activation of T cells
(C) The production of interferon
(D) The inflammation responseWhich of the following is a type of passive immunity?
(A) Natural passive immunity
(B) Artificial passive immunity
(C) Both natural and artificial passive immunity
(D) Neither natural nor artificial passive immunityWhich of the following is an example of natural passive immunity?
(A) The antibodies that a mother passes to her baby through the placenta
(B) The antibodies that a baby receives from its mother’s milk
(C) Both (A) and (B)
(D) Neither (A) nor (B)Which of the following is an example of artificial passive immunity?
(A) The antibodies that are given to a person who has been exposed to a disease
(B) The antibodies that are given to a person who is at high risk of getting a disease
(C) Both (A) and (B)
(D) Neither (A) nor (B)Which of the following is a type of active immunity?
(A) Natural active immunity
(B) Artificial active immunity
(C) Both natural and artificial active immunity
(D) Neither natural nor artificial active immunityWhich of the following is an example of natural active immunity?
(A) When a person gets a disease and their body develops antibodies to fight the disease
(B) When a person is vaccinated against a disease
(C) Both (A) and (B)
(D) Neither (A) nor (B)Which of the following is an example of artificial active immunity?
(A) When a person gets a disease and their body develops antibodies to fight the disease
(B) When a person is vaccinated against a disease
(C) Both (A) and (B)
(D) Neither (A) nor (B)Which of the following is the best way to protect yourself from diseases?
(A) Get vaccinated against diseases.
(B) Wash your hands often.
(C) Avoid contact with people who are sick.
(D) All of the above.