1 Body Defenses, Immunity & Vaccines Chapter 17

2 The Immune System Protects us from harmful agents and is made up if blood cells and the lymphatic system Part of our general body senses against disease Non-specific defenses are effective against ANY harmful agents that enter the body: skin, mucous membranes, tears, perspiration, saliva, digestive juices, sneezing, coughing, vomiting, diarrhea and fever

3 Immunity Final line of defense against disease The power of an individual to resist or overcome the effects of a particular disease or other harmful agent Immunity is SELECTIVE: Immunity to one disease does not necessarily cause immunity to another

4 Two Main Categories of Immunity I. Inborn Immunity – inherited along with other characteristics in a person’s genes S pecies Immunity – prevents certain diseases found in animals from being transmitted to humans H owever, the differences that make humans immune to these diseases make us susceptible to other diseases that do not effect lower animals M easles, Scarlet Fever & Influenza

5 Population Immunity Some groups appear to have greater inborn immunity to certain diseases than others Measles – generally mild cases in Europeans, but serious and often fatal in people of the Pacific Islands

6 Individual Immunity Where members of a certain group have a more highly developed immunity to specific diseases Some people are prone to cold sores caused by herpes virus, whereas others (possibly in the same family) have never experienced this type of infection

7 II. Acquired Immunity – develops during a person’s lifetime by encountering various, specific harmful agents 1. Antigens – any foreign substance that enters the body and induces an immune response F ound on the surface of pathogenic organisms, red blood cells, tissue cells toxins & foods S timulate the activity of certain lymphocytes (such as T-Cells)

8 2. T-Cells – come from stem cells in the bone marrow and include: C ytotoxic T-Cells – which destroy foreign cells directly I nterleukins – stimulate other lymphocytes and assist them in destroying foreign cells O ne sub-type of these cells are HELPER T-CELLS which are often infected and destroyed by the Human Immunodeficiency Virus (HIV)

9 3. Antibodies – a substance produced in response to an antigen M anufactured by “B” cells (B Lymphocytes) B Cells mature in the liver or lymphoid tissue BEFORE becoming active in the blood S ome antibodies remain in the blood to give long- term immunity S ome activated B Cells become “memory cells” & on repeated contact with an antigen, they are ready to produce antibodies immediately T his is one reason why we become immune to childhood diseases

10 III. Artificially Acquired Immunity – used when a person has not been exposed to organisms and is defenseless against heavy infection This is a protective process called IMMUNIZATION or VACCINATION Vaccines can be made with live organisms or organisms killed by heat or chemicals Live organisms MUST be weakened

11 Disorders of the Immune System 1. Allergies – a tendency to react unfavorably to the presence of certain substances that are normally harmless to most people T hese substances are called ALLERGENS P ollen, dust & dander Tissues of a susceptible person become SENSITIZED when repeatedly exposed to an allergen (antibodies are produced) N asal mucosa sensitized to pollen will have the allergic manifestation called hay fever

12 2. Acquired Immunodeficiency Syndrome (AIDS) Caused by HIV (Human Immunodeficiency Virus) Destroys “Helper Cells” Appeared in the U.S. in early 1980’s among homosexual men and intravenous (IV) drug users Currently exists in heterosexual populations of all ages New drugs can stop growth of HIV at different stages & slow onset of AIDS – but cannot cure it

13 3. Cancer It is believed that cancer cells form continuously in the body and are normally destroyed by a healthy immune system – a process called IMMUNE SURVEILLANCE As a person ages, the “surveillance” declines and cancer is more likely to develop IMMUNOTHERAPY can stimulate the immune system by removing “T” cells, activating them with interleukin and re- injecting them – some success in treating melanoma

14 4. Transplant & Rejection Natural tendency for the body to destroy foreign substances – including tissue from another human or an animal Interference with the success of transplants is called REJECTION SYNDROME Donor tissue should match recipient as closely as possible (as few antigens as possible) Drugs that suppress the immune system can leave a patient unprotected from infection