Chapter 16 Lymphatic System and Immunity PDF

Lymphatic System  Lymph: Fluid in the tissue spaces that carries protein molecules and other substances back to the blood Copyright © 2017, Elsevier Inc. All Rights Reserved. 3 Lymphatic Vessels  Permit only one-way movement of lymph ➢ Lymphatic capillaries: Tiny blind-ended tubes distribut...

Lymphatic System  Lymph: Fluid in the tissue spaces that carries protein molecules and other substances back to the blood Copyright © 2017, Elsevier Inc. All Rights Reserved. 3 Lymphatic Vessels  Permit only one-way movement of lymph ➢ Lymphatic capillaries: Tiny blind-ended tubes distributed in tissue spaces • • • • Microscopic in size Sheets consisting of one cell layer of simple squamous epithelium Poor “fit” between adjacent cells results in porous walls Called lacteals in the intestinal wall (fat transportation into bloodstream) Copyright © 2017, Elsevier Inc. All Rights Reserved. 5 Lymphatic Vessels (Cont.)  Right lymphatic duct ➢  Drains lymph from the right upper extremity and right side of head, neck, and upper torso Thoracic duct ➢ ➢ ➢ Largest lymphatic vessel Has an enlarged pouch along its course, called cisterna chyli Drains lymph from about three-fourths of the body Copyright © 2017, Elsevier Inc. All Rights Reserved. 7 Lymphedema  Swelling (edema) of tissues caused by blockage of lymphatic vessels ➢ ➢ Lymphangitis: Inflammation of lymphatic vessels, may progress to septicemia (blood infection) Elephantiasis: Severe lymphedema of limbs resulting from parasite infestation of lymphatic vessels Copyright © 2017, Elsevier Inc. All Rights Reserved. 8 Lymph Nodes     Filter lymph Located in clusters along the pathway of lymphatic vessels Lymphoid tissue: Mass of lymphocytes and related cells inside a lymphoid organ; provides immune function and development of immune cells Lymph nodes and other lymphoid organs have functions that include defense and white blood cell (WBC) formation Copyright © 2017, Elsevier Inc. All Rights Reserved. 12 Lymph Nodes (Cont.)    Flow of lymph: To node via several afferent lymphatic vessels and drained from node by a single efferent lymphatic vessel Lymphadenitis: Swelling and tenderness of lymph nodes Cancer cells can easily move through lymphatic vessels to other parts of the body in a process called metastasis Copyright © 2017, Elsevier Inc. All Rights Reserved. 16 Thymus       Lymphoid tissue organ located in mediastinum Total weight of about 35 to 40 g: A little more than an ounce Plays a vital and central role in immunity Produces T lymphocytes, or T cells Secretes hormones called thymosins, which influence T-cell development Lymphoid tissue is largely replaced by fat (during childhood) in the process called involution Copyright © 2017, Elsevier Inc. All Rights Reserved. 17 Tonsils  Composed of three masses of lymphoid tissue around the openings of the mouth and throat ➢ ➢ ➢   Palatine tonsils (“the tonsils”) Pharyngeal tonsils (also known as adenoids) Lingual tonsils Subject to chronic infection Enlargement of pharyngeal tonsils may impair breathing Copyright © 2017, Elsevier Inc. All Rights Reserved. 18 Location of Tonsils Copyright © 2017, Elsevier Inc. All Rights Reserved. 19 Spleen       Largest lymphoid organ in body Located in upper left quadrant of abdomen Often injured by trauma to abdomen Surgical removal called splenectomy Functions include phagocytosis of bacteria and old red blood cells (RBCs); acts as a blood reservoir Splenomegaly: Enlargement of the spleen Copyright © 2017, Elsevier Inc. All Rights Reserved. 20 Lymphoma   Malignant tumor of lymph nodes Two principal types: Hodgkin disease and non-Hodgkin lymphoma ➢ Cause enlarged, painless lymph nodes followed by anemia, weight loss, weakness, fever, and spread to other lymphoid tissues Copyright © 2017, Elsevier Inc. All Rights Reserved. 21 Immune System    Protects body from pathological bacteria, foreign tissue cells, and cancerous cells Made up of defensive cells and molecules Nonspecific immunity ➢ Skin: Mechanical barrier to bacteria and other harmful agents Copyright © 2017, Elsevier Inc. All Rights Reserved. 24 Nonspecific Immunity    Tears and mucus: Wash eyes and trap and kill bacteria Inflammation attracts immune cells to site of injury, increases local blood flow, increases vascular permeability; promotes movement of WBCs to site of injury or infection (chemotaxis) Signs of inflammation include heat, redness, pain, and swelling Copyright © 2017, Elsevier Inc. All Rights Reserved. 25 Inflammatory Response Copyright © 2017, Elsevier Inc. All Rights Reserved. 26 Specific Immunity   Also called adaptive immunity because of ability of body to recognize, respond to, and remember harmful substances or bacteria Inherited or inborn immunity: Inherited immunity to certain diseases from time of birth Copyright © 2017, Elsevier Inc. All Rights Reserved. 27 Acquired Immunity  Natural immunity: Exposure to causative agent is not deliberate ➢ ➢ Active: Active disease produces immunity Passive: Immunity passes from mother to fetus through placenta or from mother to child through mother’s milk Copyright © 2017, Elsevier Inc. All Rights Reserved. 28 Artificial Immunity  Exposure to causative agent is deliberate ➢ ➢ Active: Vaccination results in activation of immune system Passive: Protective material developed in another individual’s immune system and given to previously nonimmune individual Copyright © 2017, Elsevier Inc. All Rights Reserved. 29 Immune System Molecules  Antibodies ➢ ➢ ➢ Protein compounds with specific combining sites Combining sites attach antibodies to specific antigens (foreign proteins), forming an antigenantibody complex: Called humoral, or antibodymediated, immunity Antigen-antibody complexes may: • • • Neutralize toxins Clump or agglutinate enemy cells Promote phagocytosis Copyright © 2017, Elsevier Inc. All Rights Reserved. 30 Antibody Function Copyright © 2017, Elsevier Inc. All Rights Reserved. 31 Complement Proteins   Group of proteins normally present in blood in inactive state Complement cascade ➢ Important mechanism of action for antibodies • • Complement-binding sites on antibody are exposed after attaching to antigen Complement triggers a series (cascade) of reactions that produce tiny protein rings that create holes in the surface of a foreign cell Copyright © 2017, Elsevier Inc. All Rights Reserved. 32 Complement Cascade   Ultimately causes cell lysis by permitting entry of water through a defect created in the plasma membrane of the foreign cell Complement proteins play many other roles in immunity, including the inflammatory response Copyright © 2017, Elsevier Inc. All Rights Reserved. 33 Complement Cascade (Cont.) Copyright © 2017, Elsevier Inc. All Rights Reserved. 34 Immune System Cells  Phagocytes ➢ Types • • • Neutrophils: Short-lived phagocytic cells Monocytes: Develop into phagocytic macrophages and migrate to tissues Dendritic cells (DCs): Often found at or near external surfaces Copyright © 2017, Elsevier Inc. All Rights Reserved. 35 Phagocytosis {Insert Figure 16-13}} Copyright © 2017, Elsevier Inc. All Rights Reserved. 36 Phagocytes   Ingest and destroy foreign cells or other harmful substances via phagocytosis Macrophages and DCs act as antigenpresenting cells (APCs) by displaying ingested antigens on their outer surface to trigger specific immune cells Copyright © 2017, Elsevier Inc. All Rights Reserved. 37 Lymphocytes  Most numerous of immune system cells ➢ Two major types • • B cells T cells Copyright © 2017, Elsevier Inc. All Rights Reserved. 38 B-Cell Development Copyright © 2017, Elsevier Inc. All Rights Reserved. 39 Development of B Cells  First stage: Stem cells develop into immature B cells ➢ ➢ ➢ Takes place in the liver and bone marrow before birth and in the bone marrow only in adults B cells are small lymphocytes with antibody molecules (which they have synthesized) in their plasma membranes After they mature, inactive B cells migrate chiefly to lymph nodes Copyright © 2017, Elsevier Inc. All Rights Reserved. 40 Second Stage of B-Cell Development  Inactive B cell develops into activated B cell ➢ ➢ ➢ ➢ Initiated by inactive B cell’s contact with antigens, which bind to its surface antibodies, plus signal chemicals from T cells Activated B cell, by dividing repeatedly, forms two clones of cells: Plasma (effector) cells and memory cells Plasma cells secrete antibodies into blood; memory cells are stored in lymph nodes If subsequent exposure to antigen that activated B cell occurs, memory cells become plasma cells and secrete antibodies Copyright © 2017, Elsevier Inc. All Rights Reserved. 41 Function of B Cells  Indirectly, B cells produce humoral immunity ➢ ➢ ➢ Activated B cells develop into plasma cells Plasma cells secrete antibodies into the blood Circulating antibodies produce humoral immunity Copyright © 2017, Elsevier Inc. All Rights Reserved. 42 Development of T Cells  Stem cells from bone marrow migrate to thymus gland ➢ First stage: Stem cells develop into T cells • • ➢ Occurs in thymus during few months before and after birth T cells migrate chiefly to lymph nodes Second stage: T cells develop into activated T cells • • Occurs when, and if, antigen binds to T cell’s surface proteins and chemical signal received from another T cell As with B cells, clones made up of effector cells and memory cells are formed Copyright © 2017, Elsevier Inc. All Rights Reserved. 43 T-Cell Development Copyright © 2017, Elsevier Inc. All Rights Reserved. 44 Function of T Cells  Produce cell-mediated immunity ➢ ➢ ➢ Cytotoxic T cells: Kill infected or tumor cells by releasing a substance that poisons infected or tumor cells Helper T cells: Release chemicals that attract and activate macrophages to kill cells by phagocytosis; produce chemicals that help activate B cells Regulatory T cells: Release chemicals to suppress immune responses Copyright © 2017, Elsevier Inc. All Rights Reserved. 45 T-Cell Function Copyright © 2017, Elsevier Inc. All Rights Reserved. 46 Hypersensitivity of the Immune System  Hypersensitivity: Inappropriate or excessive immune response ➢ Allergy: Hypersensitivity to harmless environmental antigens (allergens) • • Immediate allergic responses usually involve humoral immunity Delayed allergic responses usually involve cell-mediated immunity Copyright © 2017, Elsevier Inc. All Rights Reserved. 47 Contact Dermatitis From Cerio R, Jackson WF: Colour atlas of allergic skin disorders, London, 1992, Mosby-Wolfe. Copyright © 2017, Elsevier Inc. All Rights Reserved. 48 Autoimmunity  Inappropriate, excessive response to selfantigens ➢ ➢ Causes autoimmune diseases Systemic lupus erythematosus (SLE): Chronic inflammatory disease caused by numerous antibodies attacking a variety of tissues Copyright © 2017, Elsevier Inc. All Rights Reserved. 49 Alloimmunity  Excessive reaction to antigens from another human ➢ ➢ May occur between mother and fetus during pregnancy May occur in tissue transplants (causing rejection syndrome) Copyright © 2017, Elsevier Inc. All Rights Reserved. 51 Immune System Deficiency  Congenital immune deficiency or immunodeficiency (rare) ➢ ➢ Results from improper lymphocyte development before birth Severe combined immune deficiency (SCID): Caused by disruption of stem cell development Copyright © 2017, Elsevier Inc. All Rights Reserved. 52 Acquired Immune Deficiency     Develops after birth Acquired immunodeficiency syndrome (AIDS): Caused by HIV infection of T cells HIV is spread by direct contact with body fluids A “cocktail” of several antiviral drugs can reduce the effects of the HIV infection Copyright © 2017, Elsevier Inc. All Rights Reserved. 53