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)

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

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

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

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

Allergy Mechanisms

Antigen (allergen)invades body

Plasma cellsproduce largeamounts of classIgE antibodiesagainst allergen

Mast cell withfixed IgEantibodies

Granulescontaininghistamine

IgE

IgE antibodiesattach to mastcells in bodytissues (and tocirculatingbasophils)

Sensitization stage

Allergy Mechanisms

More ofsame allergeninvades body

Allergenbinding to IgEon mast cellstriggers release ofhistamine (andother chemicals)

Histamine causes blood vessels to dilate andbecome leaky, which promotes edema;stimulates release of large amounts of mucus;and causes smooth muscles to contract

Subsequent(secondary)responses

Antigen

Histamine

Mast cellgranules releasecontents afterantigen bindswith IgE antibodies

Outpouringof fluid fromcapillaries

Release ofmucus

Constriction ofbronchioles

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

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 pancreatic beta 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

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

Developmental Aspects of the Lymphatic System and Body Defenses

Except for thymus and spleen, the lymphoid organs are poorly developed before birth Lymph vessels bud 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

Elephantiasis & Mastectomy Induced Edema