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Transcript
The One and Only… The Famous… IMMUNE SYSTEM!!!! What is Immune System and what is the Purpose of it? • The immune system… – is the major part of the body’s defenses. – is a specific defense that responds to the particular substances (cells, toxins, and proteins), that are known to be foreign material to the body, therefore making them unwanted. – Is intended to recognize and remove unwanted material. The Immune Response • The unique antigens on the surface of an individuals cells can distinguish “self” from “non-self” (foreign substances) and can detect and destroy the unknown material. • The immune system… – ignores the “self” cells which demonstrates tolerance. – can recognize an invader antigen as foreign, develop a specific response to that particular antigen, and then stores that response in the memory cells for future reference if incase the antigen returns. – Is assisted by general defense mechanisms (phagocytosis and the inflammatory response) to destroy foreign material. • By removing the foreign material, the immune system plays a role in preparing injured tissue for healing. – When the membrane of a malignant neoplastic cell is abnormal, the immune system might be able to identify these cells as foreign and remove them which leads to the prevention of cancer. – Unfortunately, not all cancer cells are defined as foreign causing them not to be removed from the system. Components of the Immune System • It consists of lymphoid structures, immune cells, and tissues concerned with immune cell development. • The basic structures where immune response can function are the lymph nodes, spleen, tonsils, intestinal lymphoid tissue and lymphatic circulation. A n t i g e n s • also known as immunogens • can either be foreign substances or human cell surface antigens which are very unique. • Complex proteins or polysaccharides, or even a combination of them known as glycoproteins compose most antigens. • provoke the body's immune system to produce antibodies that match the antigens to latch on and destroy them. • Antibodies- specific protein produced in humoral response to bind with antigen. • Autoantibody- antibodies against self antigen that attack own body's tissues. • Lymphatic tissue- contains many leukocytes; filters body fluids, removes foreign matter, immune response. • Bone marrow-source of stem cells, leukocytes. • Thymus- site of maturation and proliferation of T lymphocytes • The antigens are present on an individual's cell membranes. • They are coded by genes that are inherited from the parents (called major histocompatibility complex-MHC). – It is unlikey that two individuals would ever have identical antigens because since theyre inherited from the parents, they can make a large number of combination groups of genes. • MHC - activates and regulates immune response and intercellular communications. – These molecules detect changes in cell membranes caused by viruses or cancer. – Basically, If someone has a virus or something that is changing the cell, the MHC recognizes it and alters the immune system in response to the change. • Human MHC – also known as Human Leukocyte Antigen – provide close match for tissue transplantation>immune system activated by different MHC molecules>then it can tolerate self antigens and its not foreign so they dont attack. Cells… • Macrophages… – large phagocytic cells that intercept and engulf foreign material and then process and present the antigens from the foreign material to the lymphocytes thus initiating the immune response. – developed from monocytes which are part of the mononuclear phagocytic system, or reticuloendothelia system. – Secrete monokines and interleukins that play a role in activation in additional lymphocytes and in the inflammation response (secondary immune response). Lymphocytes… • white blood cell – primary cell in the immune response – produced by the bone marrow – known as immunocompetent cells when matured (cells who have special functions in recognizing and reacting with antigens) • two kinds t-cells – T-cells (cell-mediated immunity) – B-cells (humoral immunity) T-Cells – arise from stem cells in the bone marrow (process shown in chart) • Cell-mediated immunity- t-cells with protein receptors on cell surface recognize antigens on the surface of target cells and directly destroy the invading antigen – then they reproduce to create an army to battle the invader (also activate other lymphocytes both t and b), primarily affective against virus-infected calls, fungal, and protozoal infections, cancer cells, and foreign cells. • CD8 (cytotoxic) positive t-killer cells – destroy target by binding to antigen and releasing damaging enzymes (destroy target and cause inflammatory response) • CD4 (helper) positive t-cell – facilitates immune response, regulate all the cells in the immune system (b cells, t cells, macrophages, and natural killer [NK] cells, by secreting messenger cytokines) • Memory t-cells- remembers invader to activate response again if returned • B-cells – responsible for humoral immunity thorugh production of antibodies or immunoglobins. Brought to the spleen and lymphoid tissue once matured. Become antibody producing plasma cells with help from t-cells and after expose to antigens- act primarily against bacteria and viruses that are outside body • Natural killer – lymphocytes that destroy without prior exposure and sensitization, tumor cells and cells infected with viruses. Antibodies/Immunoglobulins… • An antibody is a protein complex used by the immune system to identify and neutralize foreign objects like bacteria and viruses. • Each antibody recognizes a specific antigen unique to its target. • Antibodies are found in the general circulation, forming the globulin portion of the plasma proteins, as well as in lymphoid structures. • Antibodies that recognize viruses can block directly by their sheer size. • The virus will be unable to dock to a cell and infect it, hindered by the antibody. • Antibodies that recognize bacteria mark them for ingestion by macrophages. • Together with the plasma component complement, antibodies can kill bacteria directly. • a system of proteins in the bloodstream which works in an organized fashion to defend against infecting pathogens. • These proteins work with the antibodies and phagocytes to rid the body of infection. • Complement activation also initiates an inflammatory response. • Complement – group of inactive proteins in the circulation that, when activated, stimulate that release of other chemical mediators (promote inflammation, chemotaxis , and phagocytosis). • Histamine – released from mast calls and basophils, particulary in allgeric reactions, cause vasodilatation. • Kinins – cause vasodilatation, and pain. • Leukotrienes – groups of lipids, derived from mast cells and basophils, cause contraction of bronchiolar and inflammation. • Prostaglandins – group of lipids; varied effects: inflammation, vasodilatation, and pain. • Cytokines (messengers) – stimulate activation and proliferation of b and t cells, communication b/w cells – involved in fever and leukocytosis. • Tumor necrosis factor (TNF) active in inflammatory anf immune response; stimulates fever, chemotaxis, mediator of tissue wasting, stimulates t cells, mediator in septic shock (decreasing BP) stimulates necrosis in some tumors. • Chemotactic factors – attract phagocytes to area of inflammation. Diagnostic Tests… • Tests asses the levels and functional qualities (qualitative and quantitative) of serum immunoglobulins or the measure of specific antibodies. – Identification of the antibodies are required for detecting Rh blood incompatibility or to screen for HIV infection. – Pregnant women are checked for levels of antibodies, especially for German measles. – During a hepatitis B infection, the levels of antigens and antibodies change which helps monitor the course of the infection. Diagnostic Tests cont… • The number and characteristics of the lymphocytes in the circulation can also be examined. • Extensive HLA typing is required to complete tissue matching prior to transplant procedures. The Process of Acquiring Immunity Immune Response 1. Primary response- when 1st exposed to an antigen: during exposure antigen is recognized and processed: development of antibodies or sanitized T lymphocytes is initiated. 2. Secondary response- repeat exposure to the same antigen: memory cells stimulate production of antibodies or T cells • As one ages the number of infections declines • When there are many strains of bacteria or virus causing a disease, an individual never develops antibodies to all the organisms. • Influenza- have several antigenic forms: have strains that mutate or change slightly over time: new vaccines each year. Active Immunity- when a persons own body develops antibodies or T cells. Takes a few weeks but lasts for years. Passive Immunity- Antibodies are transferred from 1 person to another. Effective immediately but only temporary protection. How is immunity acquired? Memory Natural Active Pathogens enter body and causes illness; antibodies form in host Vaccine is injected into Artificia l Active person. No illness results but Yes Person has chickenpox once Yes Person has measles vaccine and gains immunity No Placental passage during pregnancy or indigestion of breast milk. No Gammaglobulin if recent exposure to microbe antibodies form Natural passive Antibodies passed directly from mother to child to provide temporary protection Artificia Antibodies injected into a l Passive person to provide temporary protection to minimize severity of infection • Toxoid- an altered or weakened bacterial toxin that acts as an antigen in a similar manner • Booster- an additional immunization given perhaps 5 or 10 years after the initial immunization that reminds the immune system of the antigen and promotes a better secondary response. Questions 1. Differentiate between active and passive immunity? 2. Name 3 Chemical Mediators? 3. What is the immune response? 4. What is another name for antigens? 5. What are the four ways immunity is acquired?