Lecture 16
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Lecture 16. Lymphatic System and Immune Response Anatomy and Physiology JPHubbard Hartnell College – Bio11. Drain excess interstitial fluid & plasma proteins from tissue spaces Transport dietary lipids & vitamins from GI tract to the blood Produce, maintain and distribute lymphocytes.

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Lecture 16

Lecture 16

Lymphatic System and Immune Response

Anatomy and Physiology

JPHubbard

Hartnell College – Bio11


Lecture 16

  • Drain excess interstitial fluid & plasma proteins from tissue spaces

  • Transport dietary lipids & vitamins from GI tract to the blood

  • Produce, maintain and distribute lymphocytes


Lecture 16

Components of Lymphatic System

  • Lymph

    • similar to interstitial fluid

  • Vessels

    • Blind ended

  • Organs

    • red bone marrow

    • thymus

    • spleen

    • lymph nodes

  • Diffuse Tissues

    • tonsils, adenoids & peyers patches


Lecture 16

Lymphatic Vessels

  • Capillaries – similar to veins

    • Specialized to gather tissue fluid

    • In GI tract, known as lacteals -- contain chyle

  • Drain through series of trunks to 2 ducts:

    • Right lymphatic duct: right side head, arm & chest (above diaphragm)

    • Thoracic duct: Rest of body


Lecture 16

Lymphedema: swelling and consequent distention of tissue to blockage of lymphatic vessel


Lecture 16

Lymph Nodes

  • Fibrous connective covering = capsule

  • Fibrous partitions = Trabecula

  • Hilus: point of entry of blood vessels, efferent lymphatic vessel

  • Afferent vessels enters opposite hilus through cortex

  • Cortex and Medulla harbor various sorts of immune cells – site of development of specific immune response

  • Concentrated in different regions


Lecture 16

Distribution of Lymph Nodes – major areas

  • Cervical – head/neck

  • Axillary – upper limbs, mammary in F.

  • Popliteal – thigh and leg

  • Inguinal – from lower limbs

  • Thoracic – lungs, resp. and mediastinal strs.

  • Also - Nodules: Associations with digestive tract/pharynx


Lecture 16

Lymphatic Nodules

  • scattered throughout connective tissue of mucous membranes = mucosa-associated lymphoid tissue (MALT)

  • Peyer’s patches in the ileum of the small intestine

  • Appendix

  • Tonsils form ring at top of throat

    • adenoids (pharyngeal tonsil)

    • palatine tonsils (on each side wall)

    • lingual tonsil in the back of the tongue


Fig 14 08

Fig. 14.08


Lecture 16

Other Lymphatic Organs

  • Spleen

    • Lateral to stomach

    • Site of

      • exposure of blood to populations of immune cells

      • Destruction of erythrocytes

  • Thymus

    • superior to heart in mediastenum

    • Site of maturation and production of hormones which stimulate maturation of T-lymphocytes

    • Decreases in mass after adolescence


Lecture 16

Spleen

  • Largest lymphoid organ in body

  • The spleen serves two major functions in the body:

  • 1. It is responsible for the destruction of old red blood cells (RBC)

  • 2. It is a major site for mounting the immune response. The spleen behaves similarly to a lymph node but instead of filtering the lymphatic fluid it filters the blood.


Lecture 16

Disease and Immunity

  • Pathogenesis: Process by which a pathogen causes disease

    • Virus: Invade and subvert host cell metabolic processes, damage cells

    • Bacteria, Fungi, Protozoans: Produce toxins, direct tissue damage (enzymes)

    • Worms: release toxins, feed off blood, compete with host for food

    • Prions: misfolding of host proteins

  • Resistance: 2 levels

    • Innate/nonspecific

    • Adaptive/specific


Lecture 16

Innate Defenses

  • Passive:

    • Mechanical barriers

    • Chemical barriers

  • Active:

    • Interferons – hormone-like produced in response to virus infection

    • Fever

    • Inflammation

    • Defense cells

      • Phagocytes

        • Neutrophils, monocytes – become active in tissues

        • Macrophages: fixed in certain organs

      • Natural killer cells


Lecture 16

Nonspecific Defenses – Surface Barriers


Lecture 16

Natural Killer Cell at work – hole in cancer cell


Lecture 16

Complement proteins (~ 20 different ones)

  • Stimulation

    • Non-specific – by presence of foreign invader

    • Specifically – by interaction with antigen specific antibodies

  • Functions:

    • Stimulate histamine release

    • Promote phagocytosis

    • Kill bacteria through formation of membrane attack complex

    • Enhance inflammation


Lecture 16

Pathogen Specific Active Responses

  • Two Important Characteristics:

    • Specific

      • Response to specific antigen or hapten

    • Memory

      • Basis for immunization

  • Development of two cell lines

    • B-cell line

    • T-cell line


Lecture 16

Two Cell Lines – Specific Response

  • T-cells: produced bone marrow, mature in thymus

    • produce specific cytotoxic cells

    • like natural killer cells – but specific

    • Cell mediated response

  • B-cells: produced/mature in bone marrow

    • specific antibodies (immunoglobulins)

    • Humoral response


Lecture 16

Specificity

Body reacts to:

  • Antigens – a foreign substance

    • Protein, Glycoprotein, smaller molecules (hapten) bound to larger molecules

      • Toxins (poisons)

      • Molecules unique to microorganisms that are not associated with human cells

      • Altered major histo-compatibility proteins (MHC protein) identify self (‘Flag’ – friend/foe recognition)

    • 10 million  1 billion different antigens may be recognized

  • See: http://www.cat.cc.md.us/courses/bio141/lecguide/unit1/prostruct/toll/toll.html


Lecture 16

How the specific response is developed:

  • Antigen digested by macrophages / binds Virgin B cell

  • Macrophage

    • Acts as antigen presenting cell

    • Sends chemical signals which stimulate Helper T-cells division

  • Helper T cells + antigen (or antigen-MHC complex) activates multiplication of:

    T cell line  cytotoxic T cells

    B cell line  plasma cell

    production of Memory B and T cell lines


Fig 14 13

Fig. 14.13

P371-372


Lecture 16

Clonal Selection Theory

  • Diverse B lymphocytes produced during fetal development

    • Body harbors diverse population of capable of producing specific antibody w/o ever being exposed to particular antigen

  • Encounter with antigen stimulates multiplication of specific cell line; a clone from ancestral cell

    • All descendents produce same antibody


Lecture 16

Role of T cells in defending the body

  • Act like natural killer cells – but they are specific

  • Act primarily on cells

  • Kill

    • virus infected cells

    • Cancer cells

    • bacteria


Lecture 16

Role of B cells in Defending Body

  • Produce antibodies – humoral response

  • Antibodies bind to foreign antigen

    • either free or on cell surface

    • Binding may destroy antigen directly, make it a better target for phagocytes

  • Examples:

    • Toxins produced by pathogens

    • Bind bacteria, fungi, protozoan pathogens


Antibodies

Antibodies

  • 5 types –

  • IgG – main type of antibody involved in response to disease –

  • Other types:

  • IgM – involved in activation of complement

  • IgA – certain secretions, protection of digestive and resp. epith.

  • IgD – found on surface of virgin B cells

  • IgE – association with mast cells – allergic response and certain parasites


Lecture 16

How your immune system ‘remembers’:

  • Two memory cell lines are produced:

    • Memory T cells

    • Memory B cells

  • Long lived – ready to stimulate immune system to respond rapidly if the same pathogen shows up again

    • Produce effector B and T cell lines


Lecture 16

Induced Immunity – Active vs. Passive

  • Passive Immunity – occurs when individual given antibodies formed in another organism

  • Active Immunity – results in activation of body to produce its own antibodies – B and T cell lines

    • Primary immune response –

      • results in lower and transient titre

      • Important in elicitation of secondary response


Allergies immune system out of control

Allergies - Immune System out of Control?

  • Excess IgE antibodies produced

  • IgE antibodies bind to mast cells –

  • IgE antibodies interact with allergen and release histamine

  • Histamine causes swelling of blood vessels, fluid leakage

  • Type of response depends on where reactions occur and degree of reaction


Lecture 16

The End.

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