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Chapter Summary:
In this section we learned all about immunity and how our bodies fight off illness. This chapter covered subjects such as immunity and how we acquire it, the way our lymphocytes functions with our body, and diseases caused by the immune system. Our bodies acquire immunity in many different ways. This chapter also covered our defense mechanisms that our bodies use to protect us and to fight off illness.

Innate Immunity:
Our bodies use many different defense mechanisms against illness both internally and externally. Our bodies inherit some immunities through our genes. This type of immunity is called innate or nonspecific immunity. We have both internal and external defense mechanisms for innate immunity. The external defenses start with our skin which is our front line barrier against pathogens. In our digestive tract, the acid contained in our stomachs kill off many organisms while the "good" bacteria of the intestines protect us from absorbing damaging pathogens into our systems. Our respiratory tract has cillia that catches many particles that do not belong there and the mucus production that occurs in the respiratory tract helps to rid us of these particles. Our urine is highly acidic and kills off most bacteria that may be living in the genitourinary tract. In females, the vagina contains lactic acid that also helps rid our bodies of microorganisms.
Internally there are many different defense mechanisms that our bodies have but I am going to just focus on the main one of phagocytosis. Phagocytosis is "the cellular process of engulfing solid particles by the cell membrane to form an internal phagosome, phagocytes and protists." Source: Wikipedia.com. Phagocytes come in many different types. Neutrophils which are found in the blood and tissues, monocytes which are only found in the blood, macrophages which are found in all tissues, kupffer cells which are found only in the liver, alveolar macrophages which are found only in the lungs and microglia which are found only in the central nervous system. Phagocytic cells react with bacteria and they engulf the bacteria or foreign particle by forming pseudopods or "fake feet" that surround the particle. The cell ingests the particle and lysosomal enzymes digest the particle. The waste products from the particle are then released from the phagocyte by exocytosis. Below is a video that shows this process.





Antibodies:
Immunoglobulins are proteins known as antibodies. These antibodies are classified as gamma globulin plasma proteins. Antibodies are produced by B lymphocytes and are responsible for binding to antigens on the cells they are programmed to fight off. When antibodies bind to their specific antigen, they set in motion a chain of events that leads to the cell containing the antigens being destroyed. In some cases, complement proteins are activated that kill the cell containing the antigens and in other cases a process of phagocytosis is activated by the antibodies. There are five different types of antibodies. IgG is the main form of antibody that is always circulating in our system. When we are vaccinated against a disease, production on IgG antibodies in increased. The type of antibody that is found in our secretions such as saliva and breastmilk. Our allergic reactions happen thanks to the antibodies in the IgE category. IgM antibodies function as receptors to immunization antibodies. They are also secreted during a primary immune response. Another type of antibody that functions as a receptor for immunization antigens is IgD. The IgD antibodies have no other known function.

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Allergies:
Allergies represent a hypersensitivity that our bodies display to a particular antigen. The body can display an immediate hypersensitivity response or a delayed hypersensitivity response. In an immediate hypersensitivity response, the body displays symptoms such as red eyes, runny nose, red itchy skin and allergic asthma. These symptoms will present rapidly upon exposure to an allergen. In people who have no allergies to specific antigens, the allergens stimulate a response that prompts Th1 cells to secrete interferon-y and interleukin-2. These do not stimulate an allergic response. In people who are allergic to a specific allergen, Th2 cells are stimulated and they will secrete interleukin-4 and interleukin-13 which stimulate secretion of IgE antibodies which will produce an allergic response.
In a delayed allergic response, the symptoms can take hours or even days to appear. The delayed hypersensitivity response is controlled by a T lymphocyte response instead of antibodies. Delayed hypersensitivity symptoms appear due to the secretion of lymphokines instead of histamine. The most common symptom of a delayed hypersensitivity response is called contact dermatitis, which is an inflammation of the skin due to direct contact with an allergen. Below is a picture of a scratch test for delayed hypersensitivity.

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Application to Nursing:
Nurses are exposed to a wide array of communicable disease each and every time they punch in for work. Nurses are required to get certain vaccinations kin order to be on the job working. Influenza and hepatitis B are two illnesses that nurses must get vaccinated for. Some people question who staff members must get these vaccines. A nurse who understands immunity would not question why these vaccinations must occur. These vaccinations are for the staff members own protection against diseases that they could and most likely will come into contact with.
Another application of immunology that nurses come across is parents that don't understand vaccines. They don't want their children vaccinated for various reasons, sometimes they are religious reasons, and sometimes they are the parent's own ignorance. A nurse who understands the process of acquiring immunity through vaccinations would be able to explain to parents the benefits of childhood vaccines. The nurse would be able to tell the parents that when a child comes into contact with certain disease their immune system is not built up enough to fight off the disease and the child will most likely be inflicted with the disease. The nurse can explain to the parents that vaccinating children allows their immune system to be built up to fight off diseases that the child may encounter and reduce the change of the child catching the illnesses they are exposed to.

Essential Question/Case Study:

"Compare (how similar) and contrast (how different) the following categories describing the immune system: active immunity vs. passive immunity; innate immunity vs. adaptive immunity; cell-mediated immunity vs. humoral immunity. Describe the process of a local inflammatory response. Make sure to include characteristic symptoms of a local inflammation."

Active Immunity vs. Passive Immunity: Active and passive immunities are more different than they are similar. In active immunity, the person is directly injected with the antigens of a specific pathogen and the body learns to fight off that pathogen using the antibodies that it already has. In passive immunity, the person in injected with the antibodies that will fight off a specific pathogen. The similarity of the two includes the injection process. The source of the antibodies differs as well. In active immunity the antibodies come directly from the person that is being injected. In passive immunity, the antibodies can be natural as well such as in a baby acquiring antibodies from its mother or they can be from a donor. The duration of the active immunity is a long duration and can be years in length whereas passive immunity only lasts a short time such as days or weeks. Both active and passive immunity must occur before exposure to the pathogen, but only passive immunity is effective after exposure to the pathogen.

Innate Immunity vs. Adaptive Immunity: Innate and adaptive immunity are similar in that they both use antibodies to bind to antigens on foreign particles for the sake of destroying them. They both use a phagocytic process in destroying bacteria. Innate immunity is a non-specific immunity whereas adaptive immunity is a specific immunity to a particular pathogen. Each person is born with innate immunities and they include our natural defense mechanisms such as our skin, GI tract and respiratory tract. Innate immunities fight off a wide array of pathogens and foreign materials and they do not specifically attack any one type of pathogen. Adaptive immunity is an immunity that we are not born with, rather they are acquired through exposure to a particular pathogen. Adaptive immunity allows our bodies to fight off a specific pathogen when our bodies are exposed to that pathogen again after the initial exposure. Adaptive immunity creates specific antibodies that will respond to only one type of pathogen.

Cell-mediated Immunity vs. Humoral Immunity: Cell-mediated immunity and humoral immunity both involve lymphocytes to combat infections. Humoral immunity uses B Lymphocytes to combat mainly bacterial infections, but a few viral infections as well. In humoral immunity, antibodies are secreted directly into the blood and lymph within the body. Humoral immunity uses B lymphocytes and attacks infections before they attach any cells within the body. Cell-mediated immunity on the other hand uses T lymphocytes and attacks host cells that have become infected with viruses or fungi. They also attack transplant cells and cancer cells. In cell-mediated immunity, the T lymphocyte must come in direct contact or close proximity with the infected cell before it is able to destroy it because the T lymphocytes do not secrete antibodies.



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Local inflammatory response: A local inflammation begins when bacteria enters the skin through a break in the skin. After the bacteria has entered into the tissue, macrophages and mast cells release chemical that attract neutrophils responsible for phagocytosis. Complement proteints are also recruited to assist in the phagocytic process. Complement proteins attract new phagocytes and stimulate their activity. After a period of time has gone by and the phagocytes have been working hard, the B lymphocytes come in and produce antibodies against the specific antigens that they detect. Through the process of phagocytosis, neutophils kill off microorganisms and they also produce pus. Pus can be beneficial in helping to stop an infection by creating a pressure that closes off lymph and blood vessels that could otherwise spread the infection. Histamine is responsible for stimulating the vasodilation that creates the redness and warmth that is often seen with an inflammatory response. Swelling, pus, edema and pain are also usual symptoms of an inflammatory response.


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