Unit 13 Lymphatic System PDF

Unit 13 The Lymphatic System and Immunity (Chapter 23) (Ch 18: pp 401 – 403) Prepared by Wendi Roscoe...

Unit 13 The Lymphatic System and Immunity (Chapter 23) (Ch 18: pp 401 – 403) Prepared by Wendi Roscoe Fanshawe College Edited by Claudia Schubert, Ph.D., OCT Lauren Brown, MSc, WWHP Jessie Carviel, Ph.D. B.Ed. Conestoga College Copyright © 2016 by Nelson Education Ltd. 1 Lecture Outcomes 13.1 Describe the formation and function of lymph. 13.2 Explain the function of the lymph nodes, thymus, tonsils and the spleen. 13.3 Trace the path of lymph back to the venous circulation. 13.4 Describe the role of the lymphatic system in immunity and in supporting the cardiovascular system. 13.5 Describe how vaccines are produced and how they function in individual immunity. 13.6 Discuss the role of vaccines in disease transmission and how related to public health. 2  Functions of the Immune System Drains excess Transports dietary Recognizes and kills interstitial fluid from fats and fat-soluble infectious organisms, interstitial space into vitamins from the including bacteria, lymphatic vessels, small intestine to viruses, fungi, and then returns it to bloodstream parasites bloodstream Recognizes and tolerates our own Produces cells, as well as non- immunological harmful foreign memory cells that molecules such as prevent infection from food and the same organism in environmental the future substances Copyright © 2016 by Nelson Education 3 Ltd. Structure s of the Immune System Copyright © 2016 by Nelson Education Ltd. 4 Refresh: Anatomy of the Blood Vessels (and the role of the lymph vessels ) The cardiovascular system is very leaky. From capillary exchange, the body loses about 4 litres of fluid each day. To collect and recycle this fluid, the body uses a second circulatory system called the lymphatic system. Fluid in between cells is called interstitial fluid. Once this fluid enters the lymphatic vessels, it is called lymph. Ultimately the lymph re-enters the bloodstream. 5 Copyright © 2016 by Nelson Educatio n Ltd. Blood & Lymphatic Vessels Copyright © 2016 by Nelson Educatio 6 n Ltd. Lymphati c Vessels Copyright © 2016 by Nelson Education Ltd. 7  Peristalsis. The smooth muscle in the wall of the lymphatic vessels exerts slow contractions. Valves. They prevent backflow of lymph. Skeletal pump. The lymphatic Moveme vessels have valves similar to those in veins. nt of Flow through the lymphatic vessels is Lymph slow and low pressure. Lymphatic vessels can take up cells, proteins, debris etc., unlike blood vessels. They detour into lymph nodes where the lymph is cleaned and examined by immune cells for pathogens, etc. Copyright © 2016 by Nelson Education Ltd. 8 Lymphatic Ducts Copyright © 2016 by Nelson 9 Education Ltd.  Lymph nodes contain Structur immune cells that recognize and fight infections, some es of toxins, and dead cells carried in the lymph. the Lymph nodes are located in Lympha larger numbers in areas tic where microorganisms can enter the body, such as the System ears, mouth, lungs, urogenital region, and the digestive tract, as well as mammary glands. Copyright © 2016 by Nelson Education Ltd. 10 Lymph Nodes Copyright © 2016 by Nelson Education 11 Ltd. Anatomy of the Lymphatic System Bone marrow contains hematopoietic stem cells that differentiate into red and white blood cells and platelets. B cells undergo maturation process. Thymus contains thymocytes (immature T cells) that undergo a maturation process to eliminate any cells that recognize “self” antigens. Mature B and T cells that are “tolerant” of self- antigens migrate to the lymph nodes and react only to specific infections that match their specific receptors. Copyright © 2016 by Nelson Educatio 12 n Ltd.  Anatomy of the Lymphatic System Spleen Largest lymphatic organ Red pulp contains macrophages, red blood cells, and platelets; is location of breakdown of old red blood cells. White pulp contains lymphocytes, macrophages, and dendritic cells involved in the adaptive immune response. Copyright © 2016 by Nelson Education 13 Ltd. Anatomy of the Lymphatic System Lymphatic nodules Similar to lymph nodes except not surrounded by a fibrous capsule Examples: tonsils; appendix; adenoids; Peyer’s patches (located around small intestines) These are also called gut-associated lymphoid tissue (GALT) Copyright © 2016 by Nelson Educatio 14 n Ltd. Anatomy of the Lymphatic System Tonsils Pharyngeal tonsils (aka adenoids) Palatine tonsils Lingual tonsils Contain tonsillar crypts which trap unwanted materials entering the digestive and respiratory systems Image Source: Wikipedia Copyright © 2016 by Nelson Educatio 15 n Ltd. Edema Fluid accumulates in the interstitial fluid and can cause edema (swelling). Causes of fluid buildup Increased capillary hydrostatic pressure Kidneys not functioning properly Valve failure – high pressure in veins Lack of skeletal muscle contraction (clients that are bedridden) Medications Decreased plasma proteins Blocked lymphatic vessels Copyright © 2016 by Nelson Educatio 16 n Ltd.  The innate immune response includes mechanisms that prevent infection (“first line of defense”), and non-specific cellular responses to foreign cells Innate These cells will then trigger those in the adaptive immune Immune response (to be discussed next) Respons First Line of Defense: Skin and hair e Cilia and mucus Antimicrobial agents in tears, saliva, sweat Stomach acid and gut bacteria Copyright © 2016 by Nelson Education Ltd. 17 Innate Immune Response – see p 519 This is technically the “second line of defense” When body cells are infected by microorganisms (that made it past the first line of defense) they send out a chemical signal (chemotaxis) which starts the immune response Neutrophils (wbc’s) are the first to arrive and secrete chemicals called cytokines, which: attract other immune cells, secrete inflammatory molecules and phagocytize bacteria Monocytes also arrive and differentiate into macrophages and dendritic cells (phagocytize foreign cells, dead cells and cell debris) Natural killer cells puncture the walls of virus-infected cells with perforin – interstitial fluid causes cell to burst Copyright © 2016 by Nelson Educatio 18 n Ltd. Innate Immune Response Aside: when a virus infects a cell, it inserts its DNA or RNA into the cell’s DNA. When the cell replicates, new viruses are manufactured by the cell’s organelles and the viruses are released into the body Interferon (INF) is a molecule released by cells infected by viruses, which targets surrounding healthy cells These cells then produce antiviral proteins which degrade RNA, stopping the viral replication (as well as cellular replication temporarily) Complement proteins: produced by the liver and circulate in the bloodstream – are activated by an infection and: Bind to microbes and increase phagocytosis Stimulate mast cells to produce histamine + phagocytic cells Form membrane attack complex (MAC) – kill bacteria and fungi 19 Image Source: Inflammatory Response Triggered by tissues that sustain injury Chronic inflammation: tissues sustain damage from long-term exposure to immune system cytokines Implicated in many chronic diseases (cancer, diabetes, heart disease) and aging Can be in response to a poor diet, stress, and/or exposure to toxic substances Acute inflammation: healthy response to an injury (repair) or infection (kill microorganism) and promotes the regrowth of healthy new Copyright © 2016 by cells Nelson Educatio 20 n Ltd. Acute Inflammation – see p. 523 1. Foreign pathogen invades body at site of wound, activating macrophages – engulfing them and secreting cytokines and chemokines 2. This activates mast cells to release histamine 3. Histamine and cytokines vasodilate local vasculature and increase its permeability. The cytokines also make the blood vessels wall sticking, causing neutrophils to attach 4. Neutrophils respond to chemotaxis and migrate to infection site 5. Neutrophils engulf the pathogens and destroy them Copyright © 2016 by Nelson Educatio 21 n Ltd. Adaptive Immune System Called: learned response Body’s third line of defense Lymphocytes: T cells and B cells Reacts to antigens on foreign cells/pathogens and works in conjunction with cells from the innate immune system (APCs): Antigen-presenting Cells (APCs) engulf foreign cells (macrophages and dendritic cells) and then “present” the foreign cells’ antigens on their surface – recognized by the adaptive immune system Copyright © 2016 cells by Nelson Educatio 22 n Ltd. T Cells and the Cellular Immune Response All lymphocytes require activation before they can respond to antigens T cell activation requires an encounter with an antigen-presenting cell, such as a B cell or macrophage, that has already encountered a pathogen and phagocytized the antigen When T cells recognize and bind to antigenic fragments that match their receptors, they become activated Activated T cells interact directly with antigen- bearing cells; this type of cell-to-cell contact is called the cellular immune response  Types of T Cells Helper T cells stimulate B cells to produce antibodies against the displayed antigen Cytotoxic T cells monitor the body's cells, recognizing and eliminating cancer cells and virus-infected cells Cytotoxic T cells then bind to antigen-bearing cells, and release perforin, which cuts pores in the cell membrane, destroying the cells Memory T cells provide a quick response to any future exposure to the same antigen, by dividing to produce a large number of cytotoxic T cells T Cell Activities: Summary 1. Foreign pathogen enter tissues (bearing non-self antigens). 2. An accessory cell phagocytizes the antigen-bearing pathogen 3. The accessory cell then displays fragments from the digested pathogen in its membrane – i.e. the pathogen’s antigens. 4. An undifferentiated Helper T cell comes along and becomes activated if its antigen receptors fit the displayed antigen on the accessory cell. T Cell Activities: Summary 5. Once activated, the Helper T cells proliferate and: a. Interact with Cytotoxic T b.Interact with B cells and cells and release release cytokines, interleukin-2, which activate the B activating the Cytotoxic cell T cell This will then start the Activated Cytotoxic T Humoral Immune cells proliferate, Response… releasing perforin protein once they bind to surfaces of more pathogens bearing those original antigens OR turn into Memory T Cells B Cells and the Humoral Immune Response A B cell may become activated and produce a clone of cells when it encounters a foreign antigen that matches its receptors, and binds to it But most B cells need Helper T cells for activation… When a Helper T cell encounters a B cell that has already encountered and bound to a foreign antigen, the Helper T cell releases cytokines that activate the B cell (as just mentioned in the previous slide) The activated B Cell then divides and forms clones which turn into either a plasma cell, or Memory B Cell (see next slide) B Cells and the Humoral Immune Response Activated B cells will differentiate into: Plasma cells, which produce and secrete antibodies (immunoglobulins) Antibodies travel through the body fluids to attack and destroy antigens; this is called the humoral immune response Other activated B cells become Memory B cells; these remain dormant at the time, but respond to future encounters with the antigen and can be activated by helper T Cells, cytotoxic T cells and other B cells.  B Cell Activities: Summary 1. Antigen-bearing agents (pathogens) enter tissues. 2. B cell encounters an antigen that fits its antigen receptors. 3. Either alone or more often in conjunction with helper T cells, the B cell is activated. The B cell proliferates, creating clones. 4. Some of the newly formed B cells differentiate further to become plasma cells. Plasma cells synthesize and secrete antibodies whose molecular structure is similar to the activated B cell’s antigen receptors. 5. Or the clones differentiate into Memory B Cells, which lie dormant until they encounter the same pathogen in the future with that presenting antigen Functions of Antibodies Antibodies produced by the plasma cells circulate throughout the body and bind to the infecting organism – opsonization Opsonized pathogens stimulate: 1. Increase in phagocytosis by macrophages and dendritic cells 2. Increased killing by complement proteins 3. Microbes become neutralized 4. Bacteria are immobilized 5. Agglutination occurs – clumping of microbes + antibodies Copyright © 2016 by Nelson Educatio 30 n Ltd. Copyright © 2016 by Nelson Education 31 Ltd. Imager: L: rotavirus, R: rotavirus + antibodies Source: Wikimedia Commons Copyright © 2016 by Nelson Education Ltd. 32  Adaptive Immune Responses Copyright © 2016 by Nelson Education Ltd. 33 Vaccines Vaccination is the introduction of a dead or inactivated pathogen, or protein fragments into a body, and this stimulates the immune response – artificial active immunity. The vaccination will ideally trigger an immune response against that pathogen, without causing an infection. Should a person encounter that pathogen, they will have an immune reaction The memory cells the body has created because of the vaccine will recognize the pathogen and respond Copyright © 2016 by Nelson Educatio 34 n Ltd. Vaccines Live Attenuated Vaccines Live virus vaccines are prepared from attenuated strains that are almost or completely devoid of pathogenicity but are capable of stimulating an adaptive immune response. Earliest example: use of cowpox to prevent smallpox (cowpox virus is similar enough to create an adaptive immune response against the smallpox virus) Childhood MMR (measles, mumps, and rubella) Copyright © 2016 by Nelson Educatio 35 n Ltd. Vaccines Killed-Virus vaccines The outer virus proteins should be left intact, but the replicating function should be destroyed. To be effective, non-replicating virus vaccines must contain much more antigen than live vaccines. The traditional agent for inactivation of the virus is formaldehyde. Excessive treatment can destroy immunogenicity, whereas insufficient treatment can leave an infectious virus capable of causing disease. Killed-virus vaccines cannot cause the production of memory cells, but can produce antibodies – does not induce long-term immunity Examples: influenza and cholera vaccines Copyright © 2016 by Nelson Educatio 36 n Ltd. Vaccines Toxoids The mode of action of some bacteria is to produce toxins to damage our cells Toxoid vaccines are made from inactivated toxins to cause the body to create antigens and stimulate the immune system (create memory cells) They can’t cause illness for approximately 10 years – after this a booster is required to reactivate the immune system Examples: tetanus, diphtheria and pertussis (DPT) Copyright © 2016 by Nelson Educatio n Ltd. 37 Summary The function of the immune system is to maintain homeostasis by protecting the body against harmful pathogens. The functions of the lymphatic system include draining interstitial fluid and transporting dietary fats and fat-soluble vitamins. Structures include lymphatic vessels, lymph nodes, thymus, spleen, tonsils, Peyer’s patch, and bone marrow. Copyright © 2016 by Nelson Educatio 38 n Ltd. Summary The components of blood plasma, interstitial fluid, and lymph are the same; the only difference is their location. Lymph travels through the lymphatic system and is returned to the bloodstream through the subclavian veins. Lymph vessels contain valves like veins. Copyright © 2016 by Nelson Educatio 39 n Ltd.