Chapter 13 Lymphatic and Immune Systems

Transcription

1 The Chapter 13 Lymphatic and Immune Systems 1 The Lymphatic Vessels Lymphoid Organs Three functions contribute to homeostasis 1. Return excess tissue fluid to the bloodstream 2. Help defend the body against diseases 3. Absorb fats from the digestive tract and transport them to the bloodstream Lymphatic Vessels Form a one-way system Collect excess water from tissue fluid Return it to blood Fluid inside is called lymph Consists of water and solutes Lymphatic Vessels Lymphatic capillaries Found in most areas of the body Small, closed-ended vessels Lymphatic Capillaries merge into Lymphatic ducts Lymphatic ducts empty lymph into major veins Lymph is collected from tissue fluids Cleaned in the lymph nodes Returned to bloodstream tissue fluid lymphatic capillary tissue blood capillary right lymphatic duct empties lymph into the right subclavian vein right subclavian vein axillary lymph nodes Lymphoid Organs tonsil left subclavian vein Red bone marrow (Primary) Thymus (Primary) blood capillary lymphatic capillary thoracic duct Spleen (Secondary) valve Lymph nodes (Secondary) lymphatic vessel lymph node 1

2 Lymphocytes are white blood s that fight infection lobule cortex medulla tonsil lymphocyte monocyte Lymphocytes are made and/or mature in Primary lymphoid organs Red bone marrow Thymus 641 µm a. Thymus lymphatic vessel medulla b. Red bone ma rrow capsule red pulp 310 µm cortex white pulp Lymphocytes reside and fight infection in Secondary lymphoid organs Spleen Lymph nodes 641 µm capsule c. Lymph node d. Spleen 381 µm Primary lymphoid organs: Bone Marrow and Thymus Where lymphocytes are made/matured Stem s in bone marrow make immature lymphocytes Some primary lymphocytes mature in the bone and called B lymphocytes (B s) Others carried via blood to Thymus and mature there; called T lymphocytes (T s) Secondary Lymphoid Organs Where lymphocytes fight infections Spleen Blood passes through spleen Lymphocytes clean the blood of foreign particles Lymph nodes Lymph passes through lymph nodes before reaching veins Lymphocytes clean lymph; Engulf pathogens Innate and Immunity is the body s capability of removing or killing foreign substances, pathogens, and cancer s 1. Innate immunity mechanisms are fully functional without previous exposure to an unwanted substance 2. Adaptive immunity is dependent upon exposure to specific antigens Antigen: Any molecule that stimulates an immune response Innate immunity is first line of defense Non-selective: works against all foreign invaders Provided by 1. Physical and chemical barriers 2. Inflammation 3. Phagocytes and natural killer s 4. Protective proteins 2

3 Physical and Chemical Barriers Skin and mucous membranes are mechanical barriers Upper respiratory tract has cilia to remove mucus and trapped particles Oil glands in the skin secrete chemicals to weaken or kill some bacteria Stomach is acidic Normal bacteria in the intestines and other areas outcompete potential pathogens Inflammation physical or chemical damage causes inflammation Four signs Redness and heat: due to increased blood flow Swelling: due to leakiness of blood vessels Pain: due to sensitization of nerve endings Tends to wall off infections and increase exposure to immune system Skin Tissue mast histamine 1. Injured tissue s and mast s release histamine which causes capillaries to dilate and increases blood flow. Capillary 2. Macrophages and dendritic s phagocytize pathogens and release cytokines, which stimulate the inflammatory reaction. neutrophil cytokines monocyte macrophage injured tissue pathogen dendritic blood clot 4. Blood clotting walls off 3. Neutrophils and monocytes (which become capillary and prevents macrophages) squeeze through the blood loss. capillary wall and phagocytize pathogens. Phagocytes Engulf pathogen by endocytosis Neutrophils and monocytes Natural killer (NK) s Lymphocyte-like s Destroy some virus-infected s and cancer s, by -to- contact Seek out and kill all s lacking a self tag (special molecules on surface marking the s as self) Protective proteins Complement System Complement certain immune responses Form membrane attack complexes or holes in bacterial walls Fluid and salts enter the holes leading to bursting of pathogen Interferons: proteins made by virus-infected s that warn and prepare neighboring non-infected s for possible attack membrane attack complex fluids and salts complement proteins (Acquired Immunity) Induced by exposure to specific pathogens or antigens Antigens: any foreign molecule that elicits an immune response Selective: specific for the a particular invader Has Memory: remembers antigens encountered before and responds quickly and strongly to subsequent attacks 3

4 (Acquired Immunity) These defenses do not ordinarily react to our own normal s Immune system is able to distinguish self from nonself Usually take 5 to 7 days to become fully activated May last for years Adaptive defenses depend on B s and T s The two kind of s mount a dual defense against foreign molecules B Cells: secrete proteins called antibodies that circulate in blood and lymph Immunity conferred by B s called Humoral Immunity T Cells: circulate in blood and lymph and attack s infected by various pathogens such as bacteria, viruses, fungi, protozoans Immunity conferred by T s called Cellmediated Immunity Mechanism of Both B-s and T-s Capable of recognizing antigens because they have specific antigen receptors on surface Each lymphocyte has only one type of receptor Lock and key There are specific B s and/or T s for almost any antigen that can possibly threaten our system B s Give rise to plasma s which produce antibodies Antibodies combine with and neutralize particular antigens T s Do not produce antibodies Differentiate into Helper T s release chemicals to regulate immune system Cytotoxic T s attack and kill virus-infected or tumor s B s and Antibody-Mediated Immunity Antibody-mediated immunity or humoral immunity B- receptor (BCR) receptor for antigen on the surface of a B BCRs bind to antigen and activate B Activated B copies itself 4

5 Activated B rapidly divides by mitosis Most become plasma s and enter blood stream Mass production of antibodies Antibodies bind free antigens in the blood and target it for destruction by macrophages Some become memory s Long-term immunity If same antigen returns, memory B s divide and quickly give rise to more plasma s B clonal selection theory An antigen binds to the antigen receptor of only one type of B, and then this B divides, forming clones of itself Only the B with a BCR shape that fits the antigen undergoes clonal expansion Plasma s enter blood and make antibody Some B s become memory s B B- receptor antigens (BCR) Activation cytokines from T s Clonal expansion antibody Memory B s Plasma s Apoptosis Apoptosis Structure of an Antibody Antibodies are proteins also called immunoglobulins (Igs) Y-shaped Each arm has Heavy long chain Light short chain Each chain has Constant (C) regions constant within same class of antibody Variable (V) regions vary between antibodies» Binds to antigen a. antigen shape of antigen fits shape of binding site antigen-binding sites C C heavy chain light chain antigen binds to binding site C = constant V = variable Computer Model of Antibody Molecule T s and Cell-Mediated Immunity When a T leaves the thymus, it has a unique T- receptor (TCR) Unable to recognize antigen without help Must be presented to TCR by another (Antibody presenting or APC) Types of T s Helper T (T H ) s: release chemicals to regulate immune system Cytotoxic T (T C ) s: attack and kill virus-infected or tumor s 5

6 T H s only recognize antigen presented by specialized antigenpresenting s (APCs) with MHC class II molecules on their surface T C s only recognize antigen presented by various types with MHC class I molecules on their surface T- receptor (TCR) Binding to MHC-I + antigen cytokines MHC-I viral antigen Cytotoxic T Activation and clonal expansion Apoptosis T c Dendritic virus-infected Death by apoptosis Memory T Tc Cells Cell-mediated immunity against virus-infected s and cancer s T C s have storage vacuoles Perforins form pores in abnormal memebrane Granzymes induce apoptosis Some T s become memory s May live many years Can quickly jump start immune response to previous antigen cytotoxic T target (virus-infected or cancer ) Cytotoxic T vesicle perforin Perforin formshole in target. Target a. granzyme Granzymes enter through the hole and cause target to undergo apoptosis. cytotoxic T Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the Normal or Slide Sorter views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at target b. SEM 1, 250 Active Versus Passive Immunity Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the Normal or Slide Sorter views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at Adaptive immune response can be Active Individual alone produces an immune response against antigen Passive Individual is given prepared antibodies either naturally or artificially by injection 6

7 Active Versus Passive Immunity Active Versus Passive Immunity Active Immunity Develops naturally after a person is infected with an antigen Can be induced artificially immunization Vaccine substances that contain an antigen to which the immune system responds Depends on presence of memory B s and memory T s Respond quickly to antigen Passive Immunity An individual receives another person s antibodies or immune s Common natural process Cross placenta Found in breast milk Temporary because there are no memory s Used to prevent illness in an exposed individual Summary: Lymphatic system and Immunity Primary Lymphatic organs make Lymphocytes (B s and T s) Secondary Lymphatic organs serve as battlegrounds for fighting infections Swollen lymph nodes may indicate presence of infection in body Immune System: Innate immunity is first line of defense. Conferred by 1. Physical or chemical barriers in body organs 2. Inflammation in response to cuts or infections Immune response is triggered at affected site to destroy infection 3. Phagocytes (ingest microorganisms) and natural killer s (kill virus-infected s) 4. Protective proteins Immune System: Adaptive immunity Adaptive immunity is second line of defense. Conferred by B-s and T-s B-s bind to specific antigens and expand by clonal selection Make antibodies in blood to fight free antigen molecules T-s launch attack on, and kill s that are already infected Helper T-s enhance the humoral and -mediated immune responses by secreting chemicals and activating specific B-s and T-s. Cytotoxic T-s kill the infected s by to contact. 7