Immune

• Structures of the immune system

  • Bone marrow
  • Lymph nodes
  • Thymus
  • Spleen
  • Tonsils
• Hypersensitivity


  Altered immunologic response to an antigen that results in disease or damage to the host
• Types of hypersensitivity reactions

  • Immediate hypersensitivity reactions
  • Delayed hypersensitivity reactions
• Mechanisms of hypersensitivity reactions

  • Type I (IgE mediated)
  • Type II (Tissue-specific, antibody-dependent)
  • Type III (Immune complex mediated)
  • Type IV (Cell mediated)
• Complement


  Proteins in the blood that must be activated
• Type I Hypersensitivity (Allergic Reactions)


  IgE mediated, against environmental antigens (allergens), causes histamine release from mast cells
• Manifestations of Type I Hypersensitivity

  • GI allergy (vomiting, diarrhea, abdominal pain)
  • Skin manifestations (urticaria/hives)
  • Mucosa allergens (conjunctivitis, rhinitis, asthma)
  • Lung allergens (asthma, bronchospasm, edema, thick secretions)
• Rhinitis


  Reaction that causes nasal congestion, runny nose, sneezing, and itching
• Type II Hypersensitivity (Cytotoxic Hypersensitivity)


  Antibody-mediated immune reaction against cellular or extracellular matrix antigens, resulting in cellular destruction, functional loss, or tissue damage
• Type III Hypersensitivity (Immune Complex Hypersensitivity)


  Manifestations include serum sickness, Raynaud phenomenon, Arthus reaction, inflammation of small vessels, celiac disease
• Raynaud's phenomenon


  Blood vessels in hands and feet react to cold or stress, narrowing quickly and staying constricted for a long period
• Type IV Hypersensitivity (Cell-Mediated or Delayed Hypersensitivity)


  Does not involve antibody, involves cytotoxic T lymphocytes or recruitment of phagocytic cells
• Examples of Type IV Hypersensitivity

  • Graft rejection
  • Tuberculosis skin test
  • Allergic reactions from poison or metals
  • Contact dermatitis
• The tuberculin reaction is the classic example of a delayed-type hypersensitivity reaction. In response to the antigen, previously sensitized T cells release lymphokines that induce local vasodilation, edema, fibrin deposition, and recruitment of other inflammatory cells.
• Types of Transplants

  • Allograft (between individuals of same species, not identical twins)
  • Autograft (within same individual)
  • Isograft (between genetically identical twins)
  • Xenografts (between different species)
• Rejection Process


  • Hyperacute rejection (immediately after transplantation)
  • Acute rejection (several weeks after transplantation)
  • Chronic/late rejection (after months or years, involving gradual degeneration of blood vessels)
• Immunosuppressive drugs


  Must be taken continuously, but dosage must be carefully checked to prevent kidney damage. Increases risk of infection, especially by opportunistic microorganisms.
• Types of hypersensitivity reactions

  • Allergy
  • Autoimmunity
  • Alloimmunity
  • Immune deficiency
• Tolerance


  The ability of the immune system to ignore "self" cells
• Allergens


  Environmental antigens that cause atypical immunologic responses
• Anaphylaxis


  Most rapid and severe immediate hypersensitivity reaction, occurs within minutes of reexposure to antigen, systemic or cutaneous, can lead to death
• Desensitization


  May reduce the severity of the allergic reaction but could also cause anaphylaxis
• Epinephrine auto-injector (EpiPen®)


  Used in treatment of anaphylaxis
• Autoimmunity


  Breakdown of tolerance causes body to recognize self-antigens as foreign
• Systemic Lupus Erythematosus


  Most common autoimmune disease, chronic multisystem inflammatory disease with autoantibodies against nucleic acids, histones, ribonucleoproteins, and other nuclear materials
• Alloimmunity


  Reaction against another individual's tissues, can occur in transfusion reactions, transplant rejection, and during pregnancy
• Blood group antigens


  • A
  • B
  • O (neither expressed)
  • AB (both expressed)
• Transfusion Reactions


  1. ABO blood group antigens

  2. Rh blood group antigens

  3. Antibodies against foreign blood group antigens
• Systemic Lupus Erythematosus


  • Deposition of circulating immune complexes containing antibody against host DNA
  • Symptoms the result of type II or III hypersensitivity reactions
  • More common in females
• Systemic Lupus Erythematosus


  • Inflammation in multiple organs
  • Arthritis (swelling and tenderness of one or more joints)
  • Vasculitis (inflammation of the blood vessels) and rash (butterfly rash)
  • Renal disease
  • Hematologic changes
  • Cardiovascular disease
• Alloimmunity


  Reaction against another individual's tissues
• Alloantigens


  Nonself antigens from members of the same species
• Alloantigens types


  • Blood group antigens
  • Histocompatibility antigens
• Transfusion reaction occurs when person with one blood type receives another
• Type O


  Universal donor
• Type AB


  Universal recipient
• Incompatible blood transfusions result in hemolysis of erythrocytes (agglutination)
• Rh blood group


  • Antigens expressed only on RBCs
  • Rh-positive
  • Rh-negative
• Hemolytic disease of newborn


  • Rh-negative mothers with Rh-positive fetuses
  • Hemolytic means breaking down of red blood cells
  • Erythroblastosis refers to making of immature red blood cells
• Immune Deficiencies


  • Failure of immune mechanisms to function normally
  • Delayed hypersensitivity
  • Increased susceptibility to infections