Lymphatic System and Immunity:

Lymphatic System Lymph Lymphatic vessels Lymphatic tissue Lymphatic nodules Lymph nodes Tonsils Spleen Thymus

Lymphatic Vessels Carry lymph away from tissues Lymphatic capillaries More permeable than blood capillaries Epithelium functions as series of one-way valves

Functions of the Lymphatic System Fluid balance Fluid balance Excess interstitial fluid enters lymphatic capillaries and becomes lymph Excess interstitial fluid enters lymphatic capillaries and becomes lymph Fat absorption Fat absorption Absorption of fat and other substances from digestive tract Absorption of fat and other substances from digestive tract Defense Defense Microorganisms and other foreign substances are filtered from lymph by lymph nodes and from blood by spleen Microorganisms and other foreign substances are filtered from lymph by lymph nodes and from blood by spleen

Lymphatic Vessels Carry lymph away from tissues Lymphatic capillaries More permeable than blood capillaries Epithelium functions as series of one-way valves

Lymphatic Vessels Lymphatic capillaries join to form Lymphatic capillaries join to form Lymphatic vessels Lymphatic vessels Have valves that ensure one-way flow Have valves that ensure one-way flow Lymph nodes: Distributed along vessels and filter lymph Lymph nodes: Distributed along vessels and filter lymph Lymphatic trunks: Jugular, subclavian, bronchomediastinal, intestinal, lumbar Lymphatic trunks: Jugular, subclavian, bronchomediastinal, intestinal, lumbar Lymphatic ducts: Right and thoracic which connect to large veins Lymphatic ducts: Right and thoracic which connect to large veins

Lymph Drainage Into Veins

Lymphatic Tissue and Nodules Lymphatic tissue Consists mainly of lymphocytes Encapsulated or not Lymphatic nodules Numerous in loose connective tissue of digestive (Peyer’s patches), respiratory, urinary, reproductive systems

Tonsils Large groups of lymphatic nodules in nasopharynx and oral cavity Provide protection against bacteria and other harmful material Groups Palatine Pharyngeal Lingual

Lymph Nodes Organized in cortex and medulla Substances removed by phagocytosis or stimulate lymphocytes or both Only structures to filter lymph Afferent and efferent vessels

Spleen Located in left superior side of abdomen Located in left superior side of abdomen Can be ruptured in traumatic abdominal injuries resulting in bleeding, shock, death Can be ruptured in traumatic abdominal injuries resulting in bleeding, shock, death Blood flows through at 3 different rates Blood flows through at 3 different rates Fast (most), slow, intermediate Fast (most), slow, intermediate Functions Functions Destroys defective RBCs Destroys defective RBCs Detects and responds to foreign substances Detects and responds to foreign substances Limited reservoir for blood Limited reservoir for blood

Spleen

Thymus Located in superior mediastinum Divisions: Cortex and medulla Site of maturation of T cells

Immunity Ability to resist damage from foreign substances as microorganisms and harmful chemicals Ability to resist damage from foreign substances as microorganisms and harmful chemicals Categories Categories Innate or nonspecific resistance Innate or nonspecific resistance Mechanical mechanisms: Prevent entry or remove microbes Mechanical mechanisms: Prevent entry or remove microbes Chemical mediators: Promote phagocytosis and inflammation Chemical mediators: Promote phagocytosis and inflammation Cells: Involved in phagocytosis and production of chemicals Cells: Involved in phagocytosis and production of chemicals Adaptive or specific immunity Adaptive or specific immunity Specificity: Ability to recognize a particular substance Specificity: Ability to recognize a particular substance Memory: Ability to remember previous encounters with a particular substance and respond rapidly Memory: Ability to remember previous encounters with a particular substance and respond rapidly

Innate immunity

Inflammatory Response Tissue injury regardless of type can cause inflammation Tissue injury regardless of type can cause inflammation Response initiated by chemical mediators that produce vasodilation, chemotactic attraction, increased vascular permeability Response initiated by chemical mediators that produce vasodilation, chemotactic attraction, increased vascular permeability Types Types Local: Symptoms are redness, heat, swelling, pain, loss of function Local: Symptoms are redness, heat, swelling, pain, loss of function Systemic: Symptoms are increase in neutrophil numbers, fever and shock Systemic: Symptoms are increase in neutrophil numbers, fever and shock

Inflammatory Response

Normal Microcirculation Flow

Exudate Formation

Leukocyte Margination and Migration

Diapedesis

Chemotaxis

Innate Immunity: Cells White blood cells White blood cells Most important cellular components of immune system Most important cellular components of immune system Methods Methods Chemotaxis Chemotaxis Phagocytosis Phagocytosis Neutrophils Neutrophils Phagocytic and first cells to enter infected tissue Phagocytic and first cells to enter infected tissue Macrophages Monocytes that leave blood, enter tissues Large phagocytic cells Basophils and mast cells Promote inflammation Eosinophils Reduce inflammation Natural killer cells Lyse tumor and virus- infected cells

Antigenic Determinants Antigenic determinants Specific regions of a given antigen recognized by a lymphocyte Antigenic receptors Surface of lymphocyte that combines with antigenic determinant

C3a stimulates mast cells and basophils, which then secrete inflammatory mediators

Adaptive Immunity Involves the ability to recognize, respond to, and remember a particular substance Involves the ability to recognize, respond to, and remember a particular substance Stimulants Stimulants Antigens: Large molecules Antigens: Large molecules Foreign: Not produced by body, introduced from outside Foreign: Not produced by body, introduced from outside Self-antigens: Produced by body Self-antigens: Produced by body Haptens: Small molecules and capable of combining Haptens: Small molecules and capable of combining Types Types Humoral or Antibody-mediated: B cells Humoral or Antibody-mediated: B cells Cell-mediated: T cells Cell-mediated: T cells

Origin and Development of Lymphocytes B and T cells Originate in red bone marrow Move to lymphatic tissue from processing sites and continually circulate Clones are small groups of identical lymphocytes

Origin and Development of Lymphocytes Positive selection Positive selection Ensures survival of lymphocytes that react against antigens Ensures survival of lymphocytes that react against antigens Negative selection Negative selection Eliminates lymphocytes that react against self-antigens Eliminates lymphocytes that react against self-antigens Primary lymphatic organs (red bone marrow, thymus) Primary lymphatic organs (red bone marrow, thymus) Where lymphocytes mature into functional cells Where lymphocytes mature into functional cells Secondary lymphatic organs Secondary lymphatic organs Where lymphocytes produce an immune response Where lymphocytes produce an immune response

Major Histocompatability Complex (MHC) Most lymphocyte activation involves glycoproteins of cell surfaces called MHC molecules Most lymphocyte activation involves glycoproteins of cell surfaces called MHC molecules Class I molecules display antigens on surface of nucleated cells, resulting in destruction of cells Class I molecules display antigens on surface of nucleated cells, resulting in destruction of cells Class II molecules display antigens on surface of antigen-presenting cells, resulting in activation of immune cells Class II molecules display antigens on surface of antigen-presenting cells, resulting in activation of immune cells

Antigen Processing

MHC class I

Costimulation

Proliferation of Helper T Cells

Proliferation of B Cells

Lymphocyte Inhibition Tolerance: To prevent the immune system from responding to self-antigens Tolerance: To prevent the immune system from responding to self-antigens Provoked by Provoked by Deletion of self-reactive lymphocytes Deletion of self-reactive lymphocytes Preventing activation of lymphocytes Preventing activation of lymphocytes Activation of suppressor T cells Activation of suppressor T cells

Antibody-Mediated Immunity Antibodies or Immunoglobulins (Ig) Classes: IgG, IgM, IgA, IgE, IgD Structure Variable region: Part that combines with anitgenic determinant of antigen Constant region: Responsible for activities

Actions of Antibodies

Antibody Production

Cell-Mediated Immunity Antigen activates effector T cells and produces memory T cells Cytotoxic T cells lyse virus-infected cells, tumor cells, and tissue transplants Cytotoxic T cells produce cytokines, which promote phagocytosis and inflammation

Interactions and Responses of Innate and Adaptive Immunity

Ways to Acquire Adaptive Immunity

Effects of Aging Little effect on lymphatic system Little effect on lymphatic system Decreased ability of helper T cells to proliferate in response to antigens Decreased ability of helper T cells to proliferate in response to antigens Decreased primary and secondary antibody responses Decreased primary and secondary antibody responses Decreased ability of cell-mediated immunity to resist intracellular pathogens Decreased ability of cell-mediated immunity to resist intracellular pathogens

Immune System Problems Hypersensitivity reactions Hypersensitivity reactions Autoimmune disease Autoimmune disease Severe combined immunodeficiency disease (SCID) Severe combined immunodeficiency disease (SCID) Transplantation Transplantation Acute rejection Acute rejection Chronic rejection Chronic rejection