Lymphatic System and Immune Response

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Lecture 16

• Lymphatic System and Immune Response
• Anatomy and Physiology
• JPHubbard
• Hartnell College Bio11

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• 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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• 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

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• 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

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

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• 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

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• Lymphatic Nodules
• scattered throughout connective tissue of mucous
  membranes mucosa-associated lymphoid tissue
  (MALT)
• Peyers 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

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Fig. 14.08
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• 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

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• 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.

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• 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

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• 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

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Nonspecific Defenses Surface Barriers
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Natural Killer Cell at work hole in cancer cell
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• 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

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• 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

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• 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

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• 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/lecgui
  de/unit1/prostruct/toll/toll.html

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• 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

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Fig. 14.13
P371-372
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• 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

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• 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

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• 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

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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

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• 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

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• 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

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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

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The End.
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