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Lecture 22: The Lymphatic System and Immunity. Lecturer: Dr. Barjis Room P307 Phone: (718) 260-5285 E-Mail: [email protected]. Learning Objectives. Describe the structure and function of lymphatic cells, tissues and organs - PowerPoint PPT Presentation
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Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Fundamentals of
Anatomy & PhysiologyF
rederic H. M
artiniLecture 22: The Lymphatic System and Immunity
Lecturer: Dr. Barjis
Room P307
Phone: (718) 260-5285
E-Mail: [email protected]
Learning Objectives
• Describe the structure and function of lymphatic cells, tissues and organs
• List the body’s nonspecific defenses and describe the components and mechanisms of each
• Define specific resistance and distinguish between cell-mediated immunity and antibody mediated immunity
Learning Objectives
• Discuss the role of the T cell, B cell and antibodies in specific immunity
• Describe the origin, development, activation and regulation of normal resistance to disease
• Discuss the effects of stress and aging on the immune system
• The lymphatic system
• Contains cells, tissues, and organs responsible for defending the body
• Lymphocytes resist infection and disease by responding to
• Invading pathogens such as bacteria or viruses
• Abnormal body cells such as cancer cells
• Foreign proteins such as toxins
lymphatic system
The Components of the Lymphatic System
• Lymph
• Lymphatic vessels
• Lymphoid tissues and organs
• Lymphocytes and supporting phagocytic cells
The lymphatic system consists of
• Primary function is production, maintenance, and distribution of lymphocytes
• Lymphocytes must:
• Detect where problems exist
• Be able to reach the site of injury or infection
• Return of fluid and solutes from peripheral tissue to blood
• Distribution of hormones, nutrients, and waste product from their tissue of origin to general circulation.
Functions of lymphatic system
• Lymphatic capillaries
• Small lymphatic vessels
• Major lymph-collecting vessels
Lymphatic vessels include
Lymphatic Capillaries
• Superficial and deep lymphatics
• Thoracic duct
• Cisterna chyli
• Right lymphatic duct
Major lymph-collecting vessels
The Relationship between the Lymphatic Ducts and the Venous System
• Most of the lymph returns to the venous circulation by Thoracic duct
The Relationship between the Lymphatic Ducts and the Venous System
• Account for 20-30 % of circulating WBC, but body contain 10 to the power of 12 lymphocytes
• There are tree classes of lymphocytes
• T (thymus dependent) cells
• B (bone marrow-derived) cells
• NK (natural killer) cells
Lymphocytes
Lymphocytes
• Cytotoxic T cells (TC) – attack foreign cells
• Helper T cells (TH) – activate other T cells and B cells
• Suppressor T cells (TS) – inhibit the activation of T and B cells
• TH and TS cells regulates immune response
Major types of T cells
Lymphocytes
• Active B cell differentiates into
• Memory B Cell or
• Plasma B cell
• Plasma B cells synthesize and release antibody
Major types of B cells
• Lymphocyte production and maturation involves bone marrow, thymus, and peripheral lymphoid tissue
• B cells and NK cells mature in bone marrow
• T cells mature in the thymus
Lymphocyte production (lymphopoiesis)
The Derivation and Distribution of Lymphocytes
• Connective tissue dominated by lymphocytes
• Lymphoid nodules
• Lymphocytes are packed densely
• Found in the respiratory, digestive, and urinary tracts
• MALT (mucosa-associated lymphoid tissue)
• Collection of lymphoid tissues linked with the digestive system
Lymphoid tissue
Lymphoid Nodules
• Lymph nodes – function in the purification of lymph
Lymphoid organs
Lymphoid organs include: lymphoid nodes, thymus and spleen
• Located behind sternum in anterior mediastinum
• Reaches its maximum size just before puberty
• Consists two lobes• Divided into of lobules, each with a cortex and
medulla
• Lymphocytes in cortex are dividing, when mature migrate to modula and after 3 weeks enter the blood
• Secretes thymic hormones: thymosins, thymopoietins, and thymulin• stimulate stem cell division and T-cell
differentiation
The Thymus
The Thymus
• Largest mass of lymphoid tissue
• Cellular components form pulp
• Red pulp contains RBC
• White pulp similar to lymphoid nodules
• Spleen functions include
• Removal of abnormal blood cells and other blood components
• Storage of iron
• Initiation of the specific immune response
The Spleen
The Spleen
• Nonspecific defenses
• Do not distinguish one type of pathogen (e.g. bacteria) from another type
• There are 7 types of non specific defenses
• Specific defenses
• Protect against one particular threats
• Specific defense depend upon the activation of lymphocytes
Lymphatic system and body defenses
• Keep hazardous organisms outside the body
• Includes hair, epithelia, secretions of integumentary and digestive systems
Nonspecific Defenses
Physical barriers
• Remove cellular debris and respond to invasion by foreign pathogens
Nonspecific Defenses
Phagocytes
• Constant monitoring of normal tissue by NK cells
• NK cells
• Recognize cell surface markers on foreign cells
• Destroy cells with foreign antigens
• Activation of NK cells:• Recognition of unusual surface proteins
• Rotation of the Golgi toward the target cell and production of perforins
• Release of perforins by exocytosis
• Interaction of perforins causing cell lysis
Nonspecific Defenses
Immunological surveillance
Nonspecific Defenses
Immunological Surveillance)
How Natural Killer Cells Kill Cellular Targets
Nonspecific Defenses
• Interferons are small proteins that act as chemical messengers that coordinate defense
• Interferons are released by virally infected cells and activated lymphocyytes
• Interferons bind to the surface of abnormal cells and trigger the production of antiviral proteins that prevents virus proliferation.
Interferons (cytokines)
Nonspecific Defenses• There are 11 plasma complement proteins
(C)
• They are activated by:• Classical pathway
• In Classical pathway compliment binds to Ab molecule,
• Alternative pathway• In alternative pathway compliment binds to bacterial
cell
• Both pathways trigger:• Chain of reaction and result attraction of
phagocytes,
• Stimulation of phagocitic activity,
• Promotion of inflammation and
• Result puncture of bacterial cell
Complement system
Nonspecific Defenses
• Localized tissue response to injury producing
• Swelling
• Redness
• Heat
• Pain
• Effects of inflammation include
• Temporary repair of injury
• Slowing the spread of pathogens
Inflammation
Nonspecific Defenses
Inflammatory Response
Nonspecific Defenses
• Maintenance of a body temperature above 37.2oC (99oF)
• High temperature may inhibit some viruses and bacterial activities.
• It increases metabolism (1°C increase in temperature would increase metabolism by 10%)
• Pyrogens reset the hypothalamic thermostat and raise body temperature
• Pyrogen secretion is stimulated by Ag, macrophages
Fever
Specific Defenses
• Act on specific Ag only
• T-Cells are responsible for cell mediated immunity (cellular immunity) – defense against abnormal cells and pathogens inside cells
• B-cells provide Ab-mediated immunity (also called humoral immunity) – defense against Ags and pathogens in body fluid
Specific Defenses
• Innate immunity
• Genetically determined
• Present at birth
• Acquired immunity
• Not present at birth
• Achieved by exposure to antigen
• Acquired immunity can be
• Active immunity
• Passive immunity
Forms of immunity
Types of Immunity
Properties/characteristics of immunity
• Specificity – activated by and responds to a specific antigen
• Versatility – is ready to confront any antigen at any time
• Memory – “remembers” any antigen it has encountered
• Tolerance – responds to foreign substances but ignores normal tissues
The immune system response
• Antigen triggers an immune response
• Activates T cells and B cells
• T cells are activated after phagocytes exposed to antigen
• T cells attack the antigen and stimulate B cells
• Activated B cells mature and produce antibody
• Antibody attacks antigen
T cell activation
• T cells recognize Ag-glycoprotein complex in cell membrane
• Glycoproteins are synthesized in the region called Major Histocompatibility Complex (MHC)- so they are known as MHC proteins
• Each individual have different MHC proteins
• There are 2 classes of MHC proteins:
• MHC class I
• MHC class II
MHC classes• Class I – found on all nucleated cells
• They are synthesized, and transported to membrane by vesicles of golgi apparatus
• As they are formed, they pick up small peptides from the cytoplasm and take them to membrane
• If the peptides that are picked up by MHC proteins are self (belong to the body), T-cells will ignore them,
• If the peptides that are picked up by the MHC proteins are none self (do not belong to the body i.e. if they are antigens) then T-cell becomes activated anddestroy the abnormal cell.
Antigens and MHC Proteins
MHC classes
• Class II – found on antigen presenting cells and lymphocytes
• Phagocitic cells engulf pathogen
• Once the pathogen is inside the phagocitic cell, lysosome action breaks down the pathogen into fragments (Ag)
• Endoplasmic reticulum produces MHC II proteins
• Ag fragments will bound to MHC ll proteins and will be presented on the cell membrane
• MHC II and Antigen complex on the surface of membrane will activate T cells
Antigens and MHC Proteins
B cells and Antibody Mediated Response
• B cells produce specific Ab
• There are millions of B-cells - each with specific Ab on its membrane
• When B- cells are activated they can produce up to 100 million Ab per hour
Antibodies structure
• Antibodies are Y-shaped proteins consisting of:
• Two parallel polypeptide chains
• Heavy chains and light chains
• Constant region and variable region
• Antigen binding site
Antibody Structure
Antibody Structure
Actions of antibodies include:
• Neutralization
• Agglutination and precipitation
• Activation of complement
• Attraction of phagocytes
• Opsinization
• Stimulation of inflammation
• Prevention of adhesion
Classes of Antibodies (immunoglobins)
• IgG – resistance against many viruses, bacteria and bacterial toxins
• IgE – accelerates local inflammation and responsible for allergic reaction
• IgD – found on the surface of B cells
• IgM – first type secreted after antigen arrives
• IgA – primarily found in glandular sec
Primary and secondary antibody response
• Primary response
• Takes about two weeks to develop
• Produced by plasma cells
• Secondary response
• Rapid increase in IgG
• Maximum antibody titer app
Aging and the Immune Response
• Immune system becomes less effective
• Increased susceptibility to infection
• Immune surveillance declines
With age
• The structure and function of lymphatic cells, tissues and organs
• The body’s nonspecific defenses and the components and mechanisms of each
• Specific resistance, cell-mediated immunity and antibody mediated immunity
• The role of the T cell, B cell and antibodies in specific immunity
• The origin, development, activation and regulation of normal resistance to disease
• The effects of stress and aging on the immune system
You should now be familiar with: