LYMPHATIC IMMUNE SYSTEM Chapter 14

Introduction  Includes:  Network of vessels that transports fluids  Similar to cardiovascular  Organs, etc: Lymph nodes/vessels/fluid, capillaries, veins/arteries, thymus, spleen, bone marrow  Functions:  Drain interstitial fluid back to the circulatory system  Dietary lipid absorption/transport  Initiate & regulate immune responses

Flow of Lymph Flow of Lymph  Lymphatic capillaries → Lymphatic vessels → Lymphatic Trunks → Collecting Ducts → Veins  The lymph will also pass through lymph nodes found along vessels

Lymphatic Capillaries  Closed-ended tubes  Form network with blood capillaries  Thin-walled  Fluid inside is called lymph

Lymphatic Vessels and Trunks  Lymphatic vessels  Structure is very similar to veins  Lymphatic Trunks  Larger vessels than lymphatic vessels; drain into collecting ducts

Collecting Ducts  Two Main Ducts  1) Thoracic Duct- collects lymph drained from the lower limbs, abdomen, left upper limb, and left side of the thorax, head, and neck  2) Right Lymphatic Duct- collects lymph drained from right upper limb and right side of the thorax, neck, and head

Tissue Fluid  Interstitial fluid surrounding capillaries  Constant movement in and out of capillaries  Generally same composition as plasma (except doesn’t contain plasma proteins)  Some excess fluid stays in tissue and is not recollected by capillaries

Formation of Lymph  Volume pressure of interstitial fluid causes some of the fluid to enter lymphatic capillaries  Lymph will return to the bloodstream but will be filtered along the way  Removing: Wastes, pathogens, carbon dioxide

Movement of Lymph  Controlled by:  Skeletal muscle movement  Pressure changes (due to breathing)  Valves keep the movement going in one direction

Lymph Node Function  Filter foreign particles from blood before returning the lymph to the blood stream Filter foreign  Immune surveillance

Lymph Nodes (outside structure)  Usually small and bean shaped  Afferent lymphatic vessels:  Carry lymph into lymph node  Come in at various points along convex surface  Efferent Lymphatic vessels:  Carry lymph out of lymph node  Come out at hilum (area on the concave side)  Blood vessels and nerves enter at hilum

Lymph Node (Inside structure)  Connective tissue encloses lymph node and creates sub-compartments inside  Compartments are lymph nodules  Lymph sinus: space inside the nodule  Sinuses are filled with lymphocytes and macrophages

Movie

Thymus  Bilobed structure found in the chest region  Largest during childhood  Creates T-cells  Also an endocrine gland  Releases thymosins (make T-cells mature after leaving the thymus)

Spleen “blood reservoir”  Largest lymphatic organ  Found near stomach  Similar structure to lymph nodes  Sinuses contain blood instead of lymph  White pulp  High in lymphocytes  Red pulp  High in red blood cells, lymphocytes, and macrophages  Filters Blood

Immunity  Protection against pathogens  Pathogens include:  Viruses  Bacteria  Fungi  Protozoans

Types of Immunity Types of Immunity  Innate vs Adaptive  Natural vs Artificial  Active vs Passive

Innate Defenses  Species specific  First line of defense:  Skin and mucous layers  Second line of defense:  Chemical barriers Tears, gastric juices, and sweat Interferons  Fever  Inflammation  Phagocytosis

Adaptive Immunity  Third line of defense  Lymphocytes are responsible  Lymphocytes: WBCs specific for adaptive immunity  Types of lymphocytes: B and T cells  Responds to specific antigen on the invading pathogen

Cell Differentiation

Origin of Lymphocytes  Undifferentiated lymphocytes made by fetal bone marrow  T cells T cells  Lymphocytes travel to thymus and become T cells  T cells either circulate in blood or are found in lymph system  B cells  Made in marrow  B cells either circulate in blood or found in the lymph system

Differences in response Differences in response  1) Cellular Immune response  Attack up close  Performed by T cells  soldiers, destroying the invaders that the intelligence system has identified (hand to hand combat)  Signal other cells if needed for additional help  2) Humoral immune response 2) Humoral immune response  Attack from afar (produce antibodies)  Can’t destroy without T cells help  Performed by B cells  body's military intelligence system, seeking out their targets and sending defenses to lock onto them

Helper T cells  Antigen-presenting cells processes and displays antigen of pathogen  Displayed antigen must be matched with a circulating helper T cells antibody receptor  Helper T cell is activated

Cytotoxic T cells  Known as T c  Function:  Attack cells infected virus or cancerous cells  Release destructive enzymes into pathogen  Must be activated by a matching antigen

B cells  Sequence of events: 1. B cell must match with an antigen 2. Activated Helper T cell secrete cytokines 3. Cytokines make B cell proliferate to form plasma cells and memory cells 4. Plasma cell secrete antibodies

Antibodies  Globular proteins; all immunoglobulins  Contain heavy and light protein chains  Contain variable region (area that is specific to antigen – foreign body- attachment)

Antibody Types TypeFoundFunction/s IgGPlasma and tissue fluid (passed down to fetus) Activates complement system, effective against bacteria, viruses and toxins IgABreast milk (passed down to infant), tears, nasal fluid, gastric juice, intestinal juice, bile, urine Control homeostasis IgMPlasma (in response to food or bacteria) Activates complement system IgDSurface of B cells (esp. infants) Activate B cells IgEExocrine secretions (with IgA) Allergic reactions/response

Antibody Function  Two types:  1) Attack directly  Allows antibody to more easily phagocytize cells, eliminate them  Types of Direct Attack: 1. Agglutinate (Clump pathogens together) 2. Precipitate (Make pathogen insoluble) 3. Neutralize (Cover or destroy toxic part of antigen)

Antibody Function  2) Complement  Bind antigens Starts a series of rxns that activate the complements circulating in the plasma  Complement Function: Opsonization- coating antigen-antibody complex Chemotaxis- bringing macrophages to the area Lysis- rupturing membranes Agglutination Neutralization

“And the Band Played On” reaction  Get out a piece of paper:  Did you know about the AIDS struggles illustrated in the movie BEFORE watching it?  Did you find yourself angry at anytime during movie? When?  Did you find yourself sympathetic at anytime? When?  Did you find yourself sad? When?  Overall view of movie…

Memory Cells

 Memory T and B cells  Circulate after primary immune response  Body will be able to respond quickly during secondary immune response

Natural vs. Artificial Acquired Immunity  Natural:  Through exposure to pathogen  Resistance is the result of primary immune response  Artificial:  Through vaccine injection  Vaccine: bacteria or virus that has been killed or weakened Contains antigens that stimulate primary immune response Don’t produce severe symptoms of disease Ex: Measles, mumps, flu, rubella

Active vs. Passive Acquired Immunity  Naturally Acquired Active:  Occurs during pregnancy  Certain antibodies (IgG) pass from maternal blood to fetal blood  Fetus acquires limited immunity against pathogens  Artificially Acquired Passive:  Through injection of antiserum (ready-made antibodies)  Obtain from globulin proteins from people who have already developed immunity against a certain disease

Allergic Reactions Allergic Reactions  Immune response to everyday, non-harmful antigens (allergens)  Types: Delayed and Immediate  Delayed-reaction allergy:  Exposure to allergen on skin  Collects T cells and macrophages in the area  Causes dermatitis

Allergic Reactions  Immediate-reaction allergy:  Occurs within minutes  First exposure- B cells become sensitized; IgE is attached to basophils and mast cells  Subsequent exposures- mast cells and basophils secrete several substances including histamine  These substances produce the reactions seen in allergy reactions

Transplantation  Transplant tissue or organ  Ex: Organ – liver, kidney, heart; Tissue – skin, bone  New transplant tissue/organ has its own antigens  Recognized as foreign  Starts immune response (which can often reject the new transplant tissue/organ)  Tissue matching helps minimize reaction  Immunosuppressive drugs  Suppress immune reaction, avoid rejection (usually)

Autoimmunity  Cytotoxic T cells cannot correctly identify self cells and attacks self cells  Why?  Pathogen borrows self antigens during attack  Pathogen antigen is very similar to a self antigen

DisorderDescriptionSymptoms Lupus Occurs in 1 out of 2,000 Americans profound fatigue, rashes, and joint pains, severe cases: immune system attacks organs (kidney, brain, lung) Crohn’s result from intestinal inflammation diarrhea, nausea, vomiting, abdominal cramps, and pain that difficult to control Psoriasis common, affects more than 2% of Americans, often runs in families skin or body covered with buildup of red scales, skin rash Diabetes (Type 1) destruction of the insulin- producing cells of the pancreas See chapter 11 Rheumatoid arthritis immune system targets the lining (synovium) that covers various joints pain, swelling, and stiffness of the joints Multiple Sclerosis immune system targets nerve tissues of the CNS possible blindness, paralysis, and premature death Grave’s disease immune system destruction or stimulation of thyroid tissue fatigue, nervousness, cold or heat intolerance, weakness, changes in hair texture/amount, and weight gain/loss

Lymphatic System/ Water Cycle