chapter 9

• Immune system


  Complex network of cells interacting to protect the body against invasion by foreign substances
• Disorders of the immune system


  • Deficiencies of immune substances and function that affect the body's ability to ward off infection (immunodeficiency disorders)
  • Abnormal and excessive immune response to foreign substances (hypersensitivity disorders, or allergies)
  • Abnormal and excessive immune response to self (autoimmune disorders)
• Immunodeficiency


  When any one portion of the immune system is not functioning adequately
• Types of immunodeficiency


  • Primary (congenital) immunodeficiency
  • Secondary (acquired) immunodeficiency
• Primary (congenital) immunodeficiency


  • Children are born without an essential immune substance or function or with inadequate amounts of immune substances
  • Deficiencies become apparent relatively early in life
  • B-lymphocyte deficiencies may take a few months to produce symptoms due to maternal IgG protection
• Primary (congenital) immunodeficiency


  • B-Lymphocyte Deficiencies
  • T-Lymphocyte Deficiencies
  • Combined T- and B-Lymphocyte Deficiency
• Secondary (acquired) immunodeficiency


  • Loss of immune system response can occur from factors such as severe systemic infection, cancer, renal disease, radiation therapy, severe stress, malnutrition, immunosuppressive therapy, and aging
  • Can be complete or partial loss of both B- and T-lymphocyte response
• Causes of secondary (acquired) immunodeficiency


  • Severe systemic infection
  • Cancer
  • Renal disease
  • Radiation therapy
  • Severe stress
  • Malnutrition
  • Immunosuppressive therapy
  • Aging
• Stress


  Alters the immune response by stimulating the release of corticosteroids from the adrenal gland, which suppresses the inflammatory response by inhibiting macrophage action
• Immunosuppressive drugs


  Can suppress the inflammatory response
• Radiation or chemotherapy


  Can limit or destroy rapidly growing cells like T and B lymphocytes
• Extreme infection


  Can decrease immune response as the body's ability to combat infection becomes exhausted
• Malnutrition


  Can decrease immunity because rapidly growing cells need protein for synthesis; renal disease with protein loss will also deplete the amount of protein available for new lymphocyte production
• Pediatric AIDS


  • Accounts for only 1% to 2% of the total instances of AIDS
  • Transmission of HIV from mother to child by placental spread is still the most common reason for childhood HIV infection in the United States
  • Transmission can occur during pregnancy, at birth, and possibly during breastfeeding
  • Transmission has declined to less than 3% since HIV-positive women have been identified during pregnancy and prescribed antiviral therapy
  • HIV has a long incubation period of about 10 years in adults, but appears to progress more rapidly in children and infants who receive the virus through placental transmission if they do not receive treatment
  • Children who receive the virus from another source usually convert to HIV positivity by 2 to 6 weeks, or at least by 6 months after exposure
• Preliminary symptoms of HIV in children


  Poor resistance to infection, fever, swollen lymph nodes, respiratory tract infections, and thrush
• Allergic disorders


  Occur as a result of an abnormal antigen-antibody response
• Hypersensitivity


  The underlying cause of all allergic disorders, an excessive antigen-antibody response when the invading organism is an allergen rather than a simple immunogen
• Types of hypersensitivity


  • Type I (Anaphylaxis)
  • Type II (Cytotoxic Response)
  • Type III (Immune Complex)
  • Type IV (Cell-Mediated Hypersensitivity)
• Type I (Anaphylaxis)


  • IgE receptor sites attached to mast cells bind to IgE antibodies responding to an antigen, triggering mast cells to release histamine, leukotrienes, and other substances that cause vasodilation, edema, and bronchoconstriction
  • Can be triggered by insect stings, more common in boys than girls, peak season is summer
• Anaphylactic shock


  Immediate, life-threatening, type I hypersensitivity reaction that occurs after exposure to an allergen in a previously sensitized child
• Anaphylactic shock vs. Syncope


  • Anaphylactic shock: child cannot be roused, pulse and blood pressure abnormal

  Syncope: child appears pale and perspires but can be roused, pulse and blood pressure remain normal
• Type II (Cytotoxic Response)


  Immunoglobulins directly attack and destroy foreign cells without harming surrounding tissue
• Type III (Immune Complex)


  IgG- or IgE-mediated antigen-antibody complex reaction that involves complement and initiates the inflammatory response
• Type IV (Cell-Mediated Hypersensitivity)


  T lymphocytes react with antigens and release lymphokines to call macrophages into the area, causing an inflammatory response to help destroy foreign tissue
• A Mantoux or purified protein derivative (PPD) tuberculin test is an example of a type IV hypersensitivity reaction
• Type I: Immediate Hypersensitivity


  Foreign substances are detected as foreign and immunoglobulins directly attack and destroy them without harming surrounding tissue. Foreign red blood cells that are introduced to an Rh-negative woman by an Rh-positive fetus are destroyed by this process. Tumor cells may be destroyed by this process.
• Type III: Immune Complex


  An IgG- or IgE-mediated antigen-antibody complex reaction that involves complement and initiates the inflammatory response. Complement reactions that persist beyond the usual inhibition may serve as the basis for many of the autoimmune illnesses, such as glomerulonephritis and systemic lupus erythematosus. Serum sickness also occurs as a result of a type III response.
• Type IV: Cell-Mediated Hypersensitivity


  In a delayed hypersensitivity response, T lymphocytes react with antigens and release lymphokines to call macrophages into the area. An inflammatory response occurs that helps to destroy the foreign tissue. A Mantoux or purified protein derivative (PPD) tuberculin test is an example of this. Contact dermatitis is another example of a delayed hypersensitivity response.
• Contact dermatitis


  • A reaction to skin contact with an allergen (a substance irritating to the child only with prior sensitization). The first reaction is generally erythema, followed by intensely pruritic papules and then vesicles. The allergen causing the irritation is often suggested by the part of the child's body that is affected.
• Atopy


  Individuals prone to all allergic responses. Three disorders occur most frequently: hay fever (allergic rhinitis), eczema (atopic dermatitis), and asthma.
• Atopic disorders show a familial tendency, with different family members having different symptoms
• The gene responsible for an immune response is located near the human leukocyte antigen that is responsible for graft rejection
• Children whose parents smoke have a greater incidence of atopic disorders compared with children of parents who do not smoke
• Atopic dermatitis (infantile eczema)


  Primarily a disease of infants, beginning as early as the 2nd month of life and possibly lasting until the child is 2 to 3 years old. It may be related to food allergy because it tends to occur more often in formula-fed infants than in breastfed infants and is more common if infants are fed solid food before 6 months.
• Treatment of atopic dermatitis


  1. Reducing allergen exposure

  2. Reducing pruritus to prevent scratching and secondary infections

  3. Hydrating the skin

  4. Using antihistamines, corticosteroids, and antibiotics as needed
• Drug allergies


  Unpredictable symptoms occur when a drug combines with body protein to become an allergen. Allergic responses occur not with the initial administration of a drug but only after the protein interaction (hapten formation or sensitivity) has occurred.
• Food allergies


  Manifest differently from one child to another, but common symptoms include urticaria, angioedema, pruritus, stomach pain, colic, cramps, diarrhea, respiratory symptoms, and atopic dermatitis. Whole protein is probably the cause of immediate reactions; delayed reactions are probably the result of sensitivity to some protein breakdown product.
• Common foods that cause immediate allergy symptoms

  • Egg white
  • Fish and other seafood
  • Berries
  • Nuts
• Common foods that cause delayed allergy symptoms

  • Cereals (wheat and corn)
  • Milk
  • Chocolate
  • Pork
  • Legumes
  • White potatoes
  • Beef
  • Food additives and colorings
  • Oranges