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The Lymphatic System and Body Defenses

The Lymphatic System and Body Defenses. Chapter 12 Part C. Organ Transplants and Rejection. Major types of grafts Autografts – tissue transplanted from one site to another on the same person Isografts – tissue grafts from an identical person (identical twin)

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The Lymphatic System and Body Defenses

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  1. The Lymphatic System and Body Defenses Chapter 12 Part C

  2. Organ Transplants and Rejection • Major types of grafts • Autografts– tissue transplanted from one site to another on the same person • Isografts – tissue grafts from an identical person (identical twin) • Allografts – tissue taken from an unrelated person • Xenografts – tissue taken from a different animal species • Transplant recipients need to be on immunosuppressor drugs • Suppresses their system against bacteria & viruses too

  3. Organ Transplants and Rejection • Autografts and isografts are ideal donors • Xenografts of complete organs are never successful • Pig heart valves have been used with success • Allografts are more successful with a closer tissue match Video Clip: Fighting Rejection

  4. Disorders of Immunity: Allergies (Hypersensitivity) • Abnormal, vigorous immune responses • Types of allergies • Immediate hypersensitivity: • Triggered by release of histamine from IgE binding to mast cells • Reactions begin within seconds of contact with allergen; blood vessels dilate & leak; runny nose, itching • Anaphylactic shock – dangerous, systemic response • Allergen enters blood & circulates throughout body, ex. Bee sting; use epinephrine

  5. Disorders of Immunity: Allergies (Hypersensitivity) Delayed hypersensitivity • Triggered by the release of cytokines from activated helper T cells • Symptoms usually appear 1–3 days after contact with antigen (ex. Poison ivy) • Most are contact dermatitis • Antihistamines don’t work, use corticosteroids

  6. Sensitization stage Antigen (allergen)invades body Plasma cellsproduce largeamounts of classIgE antibodiesagainst allergen Mast cell withfixed IgEantibodies IgE antibodiesattach to mastcells in bodytissues (and tocirculatingbasophils) IgE Granulescontaininghistamine Allergy Mechanisms

  7. Subsequent(secondary)responses Antigen More ofsame allergeninvades body Mast cellgranules releasecontents afterantigen bindswith IgE antibodies Allergenbinding to IgEon mast cellstriggers release ofhistamine (andother chemicals) Histamine Histamine causes blood vessels to dilate andbecome leaky, which promotes edema;stimulates release of large amounts of mucus;and causes smooth muscles to contract Outpouringof fluid fromcapillaries Release ofmucus Constriction ofbronchioles Allergy Mechanisms

  8. Disorders of Immunity: Immunodeficiencies • Production or function of immune cells or complement is abnormal • May be congenital or acquired • SCID- severe combined immunodeficiency • ↓ B & T cells, live in bubble, give bone marrow transplant • Includes AIDS – Acquired Immune Deficiency Syndrome • ↓T helper cells

  9. Disorders of Immunity: Autoimmune Diseases • The immune system does not distinguish between self and nonself • The body produces antibodies and sensitized T lymphocytes that attack its own tissues • 5% of adults, 2/3 are women • Examples of autoimmune diseases • Multiple sclerosis – white matter of brain and spinal cord are destroyed • Myasthenia gravis – impairs communication between nerves and skeletal muscles • Type I diabetes mellitus– destroys pancreaticbeta cells that produce insulin • Rheumatoid arthritis – destroys joints • Graves disease – affects thyroid • Systemic lupus erythematosus (SLE)--affects kidney, heart, lung and skin • Glomerulonephritis – impairment of renal function

  10. Self Tolerance Breakdown • Inefficient lymphocyte programming • Self-reacting B or T lymphs are not eliminated, but escape into body • Appearance of self-proteins in the circulation that have not been exposed to the immune system; generally found in • Eggs • Sperm • Eye lens • Proteins in the thyroid gland • Cross-reaction of antibodies produced against foreign antigens with self-antigens • Rheumatic fever • Streptococcus bacteria antibodies cross react with heart antigens, causing valve damage

  11. Developmental Aspects of the Lymphatic System and Body Defenses • Except for thymus and spleen, the lymphoid organs are poorly developed before birth • Lymph vesselsbud from veins • See these & nodes by 5th week of gestation • A newborn has no functioning lymphocytes at birth; only passive immunity from the mother • Blocked lymphatic vessels can be caused by parasitic infection • Elephantiasis • If lymphatics are removed or lost, severe edema results, but vessels grow back in time; • ex. mastectomy

  12. Elephantiasis & Mastectomy Induced Edema

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