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Microbiology: Immune Deficiencies, Autoimmunity, and Hypersensitivities

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Terms in this set (46)

  • What is immunodeficiency?

    Immunodeficiency is a condition where the immune system's ability to fight infectious disease is compromised or entirely absent.

  • Define primary (congenital) immunodeficiency.

    Primary immunodeficiencies are congenital disorders present from birth that result in a defective immune system.

  • What is secondary (acquired) immunodeficiency?

    Secondary immunodeficiencies develop after birth due to external factors like infections, malnutrition, or medical treatments.

  • Besides aging, what is the leading cause of secondary immunodeficiencies?

    Viral infections are the leading cause of secondary immunodeficiencies besides aging.

  • Name four viruses that can cause secondary immunodeficiencies.

    HIV, measles virus, cytomegalovirus, and Epstein-Barr virus can cause secondary immunodeficiencies.

  • What is Kaposi sarcoma and which virus is associated with increased susceptibility?

    Kaposi sarcoma is a cancer of blood vessel walls; late-stage HIV infection increases susceptibility.

  • Difference between prophylactic and therapeutic immunotherapies?

    Prophylactic immunotherapy prevents disease; therapeutic immunotherapy treats existing disease.

  • Define autoimmune disorder.

    An autoimmune disorder occurs when the immune system mistakenly attacks the body’s own tissues.

  • What immune system failure leads to autoimmune disorders?

    Failure of self-tolerance causes the immune system to attack self-antigens, leading to autoimmune disorders.

  • Infectious agents possibly linked to autoimmune diseases: Type I diabetes, Guillain–Barré syndrome, Rheumatic heart disease, Multiple sclerosis?

    Type I diabetes: Coxsackievirus; Guillain–Barré syndrome: Campylobacter jejuni; Rheumatic heart disease: Streptococcus pyogenes; Multiple sclerosis: Epstein-Barr virus.

  • True or False: Autoimmune diseases are usually straightforward to diagnose with one test.

    False. Autoimmune diseases often require multiple tests and complex diagnosis.

  • What causes hypersensitivities immunologically?

    Hypersensitivities are caused by an exaggerated or inappropriate immune response to an antigen.

  • What is the hygiene hypothesis and its likely results?

    The hygiene hypothesis suggests reduced early-life exposure to microbes increases susceptibility to allergies and autoimmune diseases.

  • Name the classification system for the four types of hypersensitivities.

    The Gell and Coombs classification organizes hypersensitivities into Types I, II, III, and IV.

  • Which hypersensitivity type is not mediated by antibodies?

    Type IV hypersensitivity is cell-mediated and not antibody-mediated.

  • Define allergen and allergy.

    An allergen is a harmless antigen causing an immune response; allergy is the hypersensitive reaction to it.

  • What is sensitizing exposure in Type I hypersensitivity?

    Sensitizing exposure is the first contact with an allergen that induces IgE production without symptoms.

  • Which cells degranulate in Type I hypersensitivity and what do they release?

    Mast cells and basophils degranulate, releasing histamine, leukotrienes, and prostaglandins.

  • Difference between localized and systemic anaphylaxis?

    Localized anaphylaxis affects a specific area; systemic anaphylaxis affects the whole body and can cause shock.

  • What is anaphylactic shock and its usual treatment?

    Anaphylactic shock is a severe systemic allergic reaction treated with epinephrine.

  • What does an increased IgE titer indicate in allergy blood tests?

    Increased IgE indicates sensitization to a specific allergen.

  • What is a wheal and flare lesion in skin prick allergy testing?

    A wheal and flare is a raised, red, itchy area indicating a positive allergic reaction to the tested allergen.

  • Goal of desensitization immunotherapy?

    To reduce allergic sensitivity by gradually increasing allergen exposure to shift immune response away from IgE.

  • Which antibodies mediate Type II hypersensitivity and what do they target?

    IgG and IgM antibodies bind to antigens on cell surfaces or extracellular matrix.

  • How do non-cytolytic Type II hypersensitivity reactions occur and possible outcomes?

    Antibodies block receptor function causing altered cell activity; outcomes include cell dysfunction or death.

  • Which hypersensitivity class includes blood group incompatibility reactions?

    Type II hypersensitivity includes transfusion reactions due to blood group incompatibility.

  • What blood antigens are found on RBCs of AB- blood type?

    Both A and B antigens are present; Rh antigen is absent.

  • What happens in hemolytic transfusion reactions?

    Recipient antibodies attack donor RBC antigens, causing hemolysis and possible severe complications.

  • What occurs when a person with A+ blood receives B+ blood?

    Anti-B antibodies in recipient attack B antigens on transfused RBCs, causing hemolysis.

  • Which blood group is the universal recipient and why?

    AB+ is universal recipient because it has all A, B, and Rh antigens and no anti-A or anti-B antibodies.

  • Which blood group is the universal donor and why?

    O- is universal donor because it lacks A, B, and Rh antigens, minimizing immune reaction.

  • What happens during first pregnancy of Rh- mother with Rh+ fetus regarding HDN?

    Mother is sensitized but no hemolytic disease occurs in first pregnancy.

  • What happens during second pregnancy of Rh- mother with Rh+ fetus regarding HDN?

    Maternal anti-Rh antibodies cross placenta and cause hemolytic disease of the newborn.

  • What drug prevents Rh sensitization in Rh- mothers?

    Rho(D) immune globulin (RhoGAM) prevents sensitization to Rh antigen.

  • What antibodies mediate Type III hypersensitivity and what do they bind?

    IgG and IgM antibodies bind to soluble antigens forming immune complexes.

  • What forms and deposits in Type III hypersensitivity, and what is the result?

    Immune complexes deposit in tissues causing inflammation and tissue damage.

  • List five autoimmune diseases caused by Type III hypersensitivities.

    Lupus, rheumatoid arthritis, serum sickness, glomerulonephritis, and Arthus reaction.

  • How does serum sickness develop?

    After injection of foreign serum, immune complexes form and deposit causing systemic inflammation.

  • What mediates Type IV hypersensitivity reactions?

    T cells, especially CD4+ and CD8+ T cells, mediate Type IV hypersensitivity.

  • Why are Type IV hypersensitivities called delayed hypersensitivities?

    Because symptoms appear 24-72 hours after antigen exposure due to T cell activation.

  • List five autoimmune disorders caused by Type IV hypersensitivity.

    Type 1 diabetes, multiple sclerosis, rheumatoid arthritis, Hashimoto thyroiditis, and Crohn’s disease.

  • What molecule triggers most nonautoimmune Type IV hypersensitivities?

    Haptens, small molecules that bind to proteins and trigger T cell response.

  • List four nonautoimmune Type IV hypersensitivity reactions.

    Contact dermatitis, tuberculin skin test, graft rejection, and chronic transplant rejection.

  • Define autograft, isograft, allograft, and xenograft; which is least likely rejected?

    Autograft: self to self; Isograft: identical twin; Allograft: same species; Xenograft: different species. Autograft least likely rejected.

  • What is an immune-privileged site? Name four examples.

    Sites where immune response is limited: brain, eyes, testes, and placenta.

  • Difference between transplant rejection and graft-vs-host disease?

    Transplant rejection: host attacks graft; Graft-vs-host: graft immune cells attack host tissues.