Chapter 19: Diseases of the Immune System

• how autoimmune disorders develop

  Immune system components misidentify self-antigens as being foreign

  
  

  Autoimmune diseases develop when the body's immune system mistakenly attacks its own tissues, organs, or cells, believing them to be foreign invaders.
• Type I hypersensitiviy


  allergies

  
  

  reactions involve immunoglobin E (IgE) antibody against soluble antigen, triggering mast cell degranulation.

  
  

  IgE binds to mast cells after the first exposure
• type I hypersensitivity cellular level

  antigen-presenting cells present allergen epitopes (with MHC II) to helper cells. B cells present the same allergen epitope to TH2 cells (these release cytokines IL-4 and IL-3) and stimulate proliferation -> IgE (secreting plasma cells bind to mast cells). mast cells release chemical mediators from granules and these cause the digns of symptoms for type I reactions.

  
• Type one hypersensitivity examples:

  peanuts, pollen, allergies

  allergy-induced asthma: inhalation of allergensanaphylaxis:systemic reaction to allergenshay fever:inhalation of mold or pollenhives:foor or drug allergens, insect stings
• Type II


  Cytotoxic

  
  

  mediated by IgG and IgM antibodies binding to cell-surface antigens
• Type II hypersensitivity examples:

  Hemolytic disease of the newborn (HDN): IgG from the mother crosses the placenta, targetting the fetus' RBC for destruction

  hemolytic transfusion reactions (HTR):IgG and IgM bind to antigens on transfused RBCs, targetting the donor RBCs for destruction
• Universal Donor/Universal recipiant


  O/AB
• hemolytic transfusion reaction


  1. Donated type A blood with type A antigens enters the bloodstream of type B recipient

  2. Anti-A antibodies in plasma of type B recipient bind to the donated type A blood cells

  3. Bound anti-A antibodies activate complement cascade, causing hemolysis and the release of hemoglobin
• Type III hypersensitivities


  immune complex-mediated

  
  

  happens a lot in joints and kidneys

  
  

  reactions involve the interactions of IgG, IgM, and occasionally, IgA antibodies with antigens to form immune complexes. Accumulation of immune complexes in tissue leads to tissue damage mediated by other immune system effectors.
• immune complex


  combination of an antibody and antigen, producing a complex that can initiate a hypersensitivity reaction
• hemolytic disease of the newborn

  (HDN)problems: anti-Rh+ responsepoor oxygenated baby

  prevention:blood test parents before pregnancy, administer Rho (D) before/after each pregnancy
• type IV hypersensitivity


  T-cell-mediated reactions that can involve tissue damage mediated by activated macrophages and cytotoxic T-cells.

  
  

  exposed to allergen one time, develop sensitivity.

  
  

  example: poison ivy
• hypersensitivity types and their mechanisms

  
• hypersensitivity treatments


  desensitization- reduces the sensitivity by multiple injections of diluted allergens. Triggers an IgG response that can bind the allergen and block activation through IgEepinephrineshots - counteract the immune responseanti-inflammatory drugs- helps with milder allergic reactions (type III and type IV)
• autoimmune disorder


  cause the body's immune system to assault its own tissue as if it were a foreign invader
• organ-specific autoimmune diseases


  the damage caused by the immune reaction is seen in only one organ or one type of tissue
• organ-specific autoimmune diseases


  celiac disease- inflammatory response to gluten leads to damage of the intestine

  graves disease- immune response disrupts proper thyroid signaling (goiter (hypertrophy of the thyroid) and exophthalmia (bulging eyes) is a sign)

  Hashimoto thyroiditis

  type I diabetes- an immune response that impacts insulin production by the pancreas

  autoimmune Addison disease- immune destruction of the adrenal glands (hyperpigmentation is a sign)
• systemic autoimmune disease


  immune diseases that target multiple systems throughout the body are called systemic autoimmune diseases.
• examples of systemic autoimmune diseases:

  multiple sclerosis -central nervous system disease that affects the brain and spinal cord

  myasthenia gravis- autoantibodies against acetylcholine receptors of nerve cells

  psoriasis- a skin disease (potentially arthritis) due to cytokines produced by immune cells

  systemic lupus erythematosus- a type III hypersensitivity where autoantibodies against nuclear and cytoplasmic proteins.
• myasthenia gravis


  1. normal release of the neurotransmitter acetylcholine stimulates muscle contraction

  
  

  2. autoantibodies block the receptors for acetylcholine (AChr) on muscle cells, resulting in paralysis
• rheumatoid arthritis

  
• lupus


  a chronic autoimmune disease characterized by inflammation of various parts of the body (own DNA or proteins)

  
  

  a sign of this is butterfly rash
• allograft


  transplantation of tissue from one person to another person (homograft)

  
  

  rejection possible
• isograft


  transplant between identical twins

  
  

  little concern of rejection
• autograft


  transplantation of tissue from one area to another area on thesame individual

  no rejection concerns
• xenograft


  transplantation of tissue from an animal to a human

  
  

  rejection possible
• graft versus host disease (

  transplanted tissue can produce immune cells, you can develop graft-versus-host disease, associated with bone marrow transplants
• the only tissue that can produce its own immune cells

  bone marrow
• to minimize a graft-versus-host disease, _______ are matched from the donor to the recipient.

  human leukocyte antigens
• immunodeficiency


  when immune defenses are absent or ineffective
• primary immunodeficiency


  caused byinheriteddefects to the immune system

  examples:Chronic granulomatous disease -phagocytic cells don't kill pathogens

  X-linked agammaglobulinemia- B-cells don't produce antibodies correctly

  Selective IgA deficiency -cannot produce IgA antibodies (making lung and gastrointestinal infections common)

  Severe combined immunodeficiency disease (SCID) -both T and B-cell deficiencies, often fatal
• SCID


  severe combined immunodeficiency disease

  
  

  bubble boy
• Secondary Immunodeficiency


  caused by an acquired problem with B and/or T-cells

  Systemic disorders -diabetes mellitus, malnutrition, hepatitis, or HIV infection

  Immunosuppressive treatments -cytotoxic chemotherapy, bone marrow ablation, radiation therapy
• primary and secondary immunodeficiencies

  
• immunodeficiency treatments


  -Antibiotic therapy

  -Injection of IV/SQ immunoglobulin

  -Bone marrow transplant

  
  

  **passive immunity
• passive immunity


  the short-term immunity that results from the introduction of antibodies from another person or animal.
• tumor


  a group of cells that have lost contact inhibition and grow on top of each other. may be benign (not cancerous) or malignant (cancerous)
• cancer


  diseases due to loss of cell-cycle regulation that leads to cell proliferation
• cancer treatment: cell-mediated response to tumors

  abnormal tumor cells can be targeted by immune cells
• cancer treatment: cancer vaccines

  can be preventative (target viral causes of cancer) or therapeutic (may use the immune system to target cancer cells)

  risks:- immune response may not target not only the tumor but also healthy tissue- allergic/adverse reactions to the injection- vaccines may not induce an immune response in all individuals

  benefits:- enhances immune response, the immune system recognizes and targets tumor cells, leading to tumor regression or prevention or tumor reoccurrence.- vaccines can targetspecificantigens- immunological memory