The Lymphatic System and Immunity

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The Lymphatic System and Immunity
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Functions of LS

• Absorption of excess tissue fluid
• Absorption of fat from intestines
• Defense of body from infection and disease

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Structures of the LS

• Lymphatic vessels
• Lymph Nodes
• Lymphoid organs

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I. Lymphatic Vessels

• Carry Lymph

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I. Lymphatic Vessels

• Similar to veins
• Contain valves
• From tissues lymphatic capillaries take fluid
  back toward Vena Cava

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Lymph

• Interstitial fluid (tissue fluid) forced out of
  capillaries
• Resembles plasma but with less proteins

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Lymph nodes

• Also sometimes referred to as lymph glands, lymph
  nodes are small rounded or bean-shaped masses of
  lymphatic tissue surrounded by a capsule of
  connective tissue.
• Lymph nodes filter the lymphatic fluid and store
  special cells that can trap cancer cells or
  bacteria that are traveling through the body in
  the lymph fluid.
• The lymph nodes are critical for the bodys
  immune response and are principal sites where
  many immune reactions are initiated.
• During a physical examination, doctors often look
  for swollen lymph nodes in areas where lymph
  nodes are abundant, including the neck, around
  the collarbone, the armpit (axilla), and the
  groin.

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Lymphoid organs

• Have a surrounding fibrous capsule
• Separates it from surrounding tissue
• Filters lymph fluid
• Examples
• Lymph nodes
• Thymus
• spleen

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III. Lymphoid Tissues

• Made of Connective tissue and lymphocytes
• 2 types
• A. Lymphoid Nodules
• B. Lymphoid organs

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Lymphoid nodule

• Filters surrounding tissue fluid not lymph
• Examples
• Tonsils
• Pharyngeal
• Palatine
• lingual

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Thymus

• T Cell Maturation
• Produces hormones
• Thymosins

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Spleen

• Located near stomach
• Removes abnormal blood cells
• Stores iron from recycled RBCs
• Monitors and responds to pathogens and foreign
  antigens in body

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Lymphocytes

• Make up 25 of WBCs in blood
• Most found outside of BVs
• 3 main types
• T cells (T for thymus)
• B cells (B for Bone marrow)
• NK cells (natural killers cells)

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Lymphocytes
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T cells

• Originate in Bone Marrow
• Mature in Thymus
• Make up 75 of lymphocytes
• Several different types of
• T cells with different functions

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B cells

• Originate in BM
• Mature in BM
• Make up 12.5 of lymphocytes
• Mature into plasma cells which secrete soluble
  proteins, called antibodies or immunoglobulins

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NK cells

• Originate in BM
• Make up 12.5 of lymphocytes
• Readily attack foreign cells, infected cells and
  abnormal cells
• Responsible for immunological surveillance

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Defense Mechanisms

• Specific
• Non-specific (general)

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Non-specific Defense

• Present at birth
• Do not discriminate between one threat or another
• Deny entrance or limit the spread of
  microorganisms or other environmental hazards

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Non-specific Defense

• Physical barriers
• Phagocytic cells
• Immunological surveillance
• Interferon
• Complement
• Inflammation
• Fever

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Physical barriers

• Skin
• Hair
• Tears
• Sweat and sebaceous galnds
• Mucus
• Stomach acid
• Urine
• Reproductive secretions

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Phagocytic cells

• Engulf other cells
• 2 classes
• Microphages neutrophils and eosinophils
• Macrophagesmonocytes

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Immunological Surveillance

• NK cells are sensitive to changes in cell
  membranes, usually associated with
• Cancer cells
• Viral infections

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Immunologically Important Proteins

• Interferon
• Complement

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Interferon

• Released by activated lymphocytes and M?s or by
  viral infected cells
• Causes cells to make proteins that interfere with
  viral reproduction

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Complement

• Supplements the actions of Abs
• Enhances phagocytic action
• Destroys cell membranes
• Promotes Inflammation

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Inflammation

• Localized tissue response to injury
• Symptoms
• Swelling
• Redness
• Heat
• pain

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Inflammation

• Produced by any stimulus that damages cells or
  connective tissue
• Mast cells found in CT releases histamine and
  heparin to initiate inflammation
• Stops pathogens from leaving scene of the crime
• Promotes their removal and repair of damage

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Fever

• Continued body temp gt 99oC
• Body temp controlled hormonally
• Harmful
• Too high may damage tissues/organs
• Beneficial
• promotes activity of immune cells

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Specific Defense

• Provides protection from threats on individual
  basis
• Also called IMMUNITY

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Specific Defense (immunity)

• Resistance to injuries/disease caused by specific
  antigens or chemicals (toxins)
• 2 types
• Innate
• Inherited or inborn immunity
• Acquired
• Passive
• Active

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Passive Acquired Immunity

• Short term
• Receipt of antibodies produced by someone else
• Injected
• Fetal development or breast feeding

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Active Acquired Immunity

• Long term
• Results from exposure to Ag
• 2 origins
• Accidental/natural
• Artificial/vaccination

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Immune response

• GOAL to destroy or inactivate pathogens,
  abnormal cells or foreign molecules (toxins)
• RESULT immunity
• Types of response
• Cell-mediated
• Ab-mediated (humoral)

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T cell Immunity

• Once activated, cells divide and differentiate
  into 4 types
• Cytotoxic T cells
• Memory T cells
• Suppressor T cells
• Helper T cells

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B cell Immunity

• Activated by exposure to Ag or chemicals released
  by Helper T cells (Interleukins)
• Cells divide and differentiate into 2 types of
  cells
• Plasma Cells
• Memory B cells

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Primary vs Secondary Immune response

• Primary
• Results from initial exposure to Ag
• Takes 7-10 days for response
• Response (abs, cells, etc) peaks after several
  weeks

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Primary vs Secondary Immune response

• Secondary
• Respnse that results from 2nd exposure to same Ag
• Tales 1-3 days for response to peak
• Stronger and longer response

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Primary vs Secondary
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