Biology 2 Chapter 42 Notes (pt. 1)
Biology 2 Chapter 42 Notes (pt. 1) BIOL 1040
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This 6 page Class Notes was uploaded by Courtney Luber on Thursday March 10, 2016. The Class Notes belongs to BIOL 1040 at Clemson University taught by Dr. William Surver in Fall 2016. Since its upload, it has received 18 views. For similar materials see General Biology II in Biology at Clemson University.
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Date Created: 03/10/16
Chapter 42—The Immune System Intro o Barriers—skin, mucous membranes o Nonspecific internal defenses (innate)—phagocytosis (certain cells will consume & destroy invader), natural killer cells (cells that have the ability to kill foreign invaders), inflammation, fever Very fast-acting o Specific internal defenses (acquired)—cell-mediated immunity (cells attack invader), humoral immunity (chemical immunity; form antibodies against invader) Takes a little bit of time to activate Innate Immunity o A series of defenses that Act immediately upon infection Are the same whether the pathogen has been encountered before o Invertebrates rely solely on innate immunity which may consist of Exoskeleton (i.e. arthropods) Low pH Enzymes – lysozyme (enzyme that acts against a certain pathogen) Immune cells capable of phagocytosis, cellular ingestion and digestion of foreign substances o Vertebrates have innate and adaptive immunity o Innate immunity in vertebrates includes Skin and mucus membranes Interferons Neutrophils (blood cells) – phagocytic cells Natural killer cells that attack cancer cells and virus- infected cells Macrophages (very large blood cells) Complement system (body creates this to fight disease) o Tissue damage triggers the inflammatory response Purposes of inflammatory system: Can disinfect and clean infected tissues Limit the spread of infection to surrounding tissues o Bacterial infections can bring about an overwhelming systemic inflammatory response leading to septic shock High fever and low blood pressure o Inflammation may be localized or widespread Best to keep it localized because if it is widespread, the entire body is seeing these bacteria o Sometimes microorganisms get into the blood or release toxins that are carried throughout the body in the bloodstream o Bacterial infections can bring about an overwhelming system inflammatory response leading to septic shock, characterized by very high fever and low blood pressure. Adaptive Immunity o Adaptive immunity (acquired immunity) is a set of defenses found only in vertebrates that is activated only after exposure to certain pathogens o We have cells that are made to remember what each pathogen is o Our body knows which cells are ours o Autoimmune diseases—body does not recognize own cells o Unlike innate immunity, it differs from individual to individual depending on what pathogens they have previously been exposed to. o Antigens are Any molecule that elicits an adaptive immune response Are nonself molecules that protrude from pathogens or other particles such as viruses, bacteria, mold, spores, pollen, house dust or cell surfaces of transplanted organs o When the immune system detects an antigen it responds with an increase in the number of cells that either attack the invader directly or produce immune proteins called antibodies o Antibodies are proteins found in blood plasma that attach to one particular kind of antigen and help counter its affects o Adaptive immunity has remarkable memory o Remembers antigens that it has encountered before sometimes decades earlier and react against them more quickly and vigorously on subsequent exposures. o Lymphocytes are white blood cells that spend most of their time in the blood and tissues and organs of the lymphatic system o Are responsible for adaptive immunity o Provide specialized defenses that act on pathogens located in either the body fluids or inside cells o Adaptive immunity is usually obtained by natural exposure to antigens but it can be achieved by vaccination also known as immunization o The immune system is confronted with a vaccine composed of a harmless variant or part of a disease-causing microbe, such as an inactivated bacterial toxin a dead or weakened virus or a piece of a virus. o Whether antigens enter the body naturally or artificially the resulting immunity is called active immunity because the person’s own immune system actively produces antibodies o It is also possible to acquire passive immunity by receiving premade antibodies Lymphatic System o Involved in innate and adaptive immunity o Consists of a branching network of Lymphatic vessels Lymph nodes—present in various places (i.e. underneath arms); filter out things like bacteria Lymph which is similar to the interstitial fluid that surrounds body cells but contains less oxygen and fewer nutrients o Lymphatic vessels Collect fluid from body tissues Return it as lymph to the blood o The lymphatic system thus has two main functions To return tissue fluid back to the circulatory system Fight infection o As lymph circulates through lymphatic organs it Collects microbes, parts of microbes, and microbial toxins Transports them to lymphatic organs where macrophages engulf the invaders and lymphocytes may mount an adaptive response Adaptive Immunity o Our immune system reacts to foreign molecules called antigens, which elicit the adaptive (acquired) immune response o Virtually anything can be antigenic to you o The adaptive immune system Found only in vertebrates Reacts to specific pathogens (antigens) “Remembers” an invader o Lymphocytes (WBCs) are responsible for adaptive immunity o All blood cells originate from stem cells in the bone marrow B lymphocytes (B cell) continue to develop in the bone marrow T lymphocytes (T cells) develop further in the thymus o By mounting a dual defense, B and T cells defend against infections in body fluids and those inside cells o Self vs. non-self Self—our ability to respond to things that are us MHC markers: attached to cell membrane; label our cells; unique to us; tells us that things belong to us Non-self—our ability to respond to things that aren’t us Cell engulfs antigen; marker marks cell as antigenic; becomes non-self o When a B cell develops in bone marrow or a T cell develops in the thymus, the cells differentiate from other cells by synthesizing many copies of a specific protein called antigen receptors, capable of binding one specific type of antigen, which are then incorporated into the plasma membrane o All antigen receptors on the surface of a single lymphocyte are identical and recognize a particular antigen o o Specificity (different antigen receptors) ^^^ o The B cells and T cells of the adaptive immune response provide a two-pronged defense; combat pathogens both in the body fluids and inside body cells o B cells Participate in the humoral immune response Defend against bacteria and viruses present in body fluids Secrete antibodies into the blood and lymph o T cells Participate in the cell-mediated immune response Defend against infections inside body cells Attack cells infected with bacteria or viruses Promote phagocytosis by other white blood cells and by stimulating B cells to produce antibodies o Some T cells play a part in both the cell-mediated and humoral immune responses o Antigen receptors and antibodies bind to specific regions on an antigen o Both the humoral and cell-mediated immune responses are initiated when lymphocytes recognize antigens B cells bind antigens directly T cells require an additional step for recognition o Antigens usually do not belong to the host animal o Most antigens are proteins or large polysaccharides that protrude from the surfaces of viruses or foreign cells o Common examples are Protein coat molecules of viruses Parts of capsules and cell walls of bacteria Macromolecules on the surface cells of other kinds of organisms protozoans and parasitic worms o Antigen receptors and antibodies bind to specific regions of an antigen o Antigenic determinants Specific regions on an antigen where antibodies bind Sometimes called epitopes o Antigen receptors on B cells as well as antibodies recognize and bind to the antigenic determinant o The specific region of an antigen receptor or antibody that recognizes and antigenic determinant in the antigen-binding site The binding site and antigenic determinant have shapes like a lock and key An antigen usually has several different determinants o The humoral and cell-mediated immune responses both defend against a variety of antigens through a process known as clonal selection o Inside the body an antigen encounters a diverse pool of B and T lymphocytes; one particular antigen interacts only with a fraction of lymphocytes, those bearing receptors that are specific to that antigen o Once activated by the antigen the lymphocytes proliferate forming a close of thousands of cells selected to recognize and respond to the antigen Some of these cells called effector cells act immediately to combat infection Others know as memory cells lie in wait to help activate the immune system upon subsequent exposure to the antigen o Steps of Clonal Selection Antigens bind to a B cell that has corresponding antigen receptors B cells with different antigen receptors are unaffected by this antigen The selected B cell gives rise to a clone of B cells with antigen receptors for the same antigen Some B cells become effector cells called plasms cells, which secrete antibodies into the blood an lymph Antigens bound by antibodies are destroyed by innate defenses, such as macrophages Some B cells become memory cells o Primary vs. secondary immunity The primary response occurs upon the first exposure to an antigen and is slower than the secondary response The secondary response occurs upon a second exposure to an antigen and is faster stronger than the primary immune response o The secondary response like the primary, activates both effector cells and memory cells o Antibodies Secreted into the blood and lymph by effector B cells Are Y-shaped and have two antigen-binding sites specific to the antigenic determinants that elicit its secretion o Antibodies promote antigen elimination through several mechanisms Neutralization-binding to surface proteins on a virus or bacterium and blocking its ability to infect a host Agglutination-using both binding sites of an antibody to join invading cells together into a clump Precipation-similar to agglutation except that the molecules link dissolved antigen molecules together Activation of the complement system o
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