cytotoxic hypersensitivity

Examples of cytotoxic hypersensitivity in the following topics:

• Type II (Cytotoxic) Reactions

  • In type II (cytotoxic) hypersensitivity, the antibodies produced by the immune response bind to antigens on the patient's own cell surfaces.
  • In type II hypersensitivity (or cytotoxic hypersensitivity), the antibodies produced by the immune response bind to antigens on the patient's own cell surfaces.
  • Another form of type II hypersensitivity is called antibody-dependent cell-mediated cytotoxicity (ADCC).
  • Autoimmune diseases resemble type II-IV hypersensitivity reactions.
  • They differ from hypersensitivity reactions in that the antigens driving the immune process are self-antigens rather than non-self as in hypersensitivity reactions.

• Hypersensitivity

  • A hypersensitivity reaction refers to an overreactive immune system triggered by allergies and autoimmunity.
  • Hypersensitivity (also called hypersensitivity reaction) refers to undesirable reactions produced by the normal immune system, including allergies and autoimmunity, and are commonly mediated by antibodies.
  • Hypersensitivity reactions require a pre-sensitized (immune) state of the host .
  • Cytotoxic Hypersensitivity (Type II) is an immune response to human cells with foreign antigens.
  • The common effects of Poison Ivy are the result of Type IV hypersensitivity.

• Type IV (Delayed Cell-Mediated) Reactions

  • Type IV hypersensitivity reactions are cell-mediated and take 2 to 3 days to develop.
  • Cell-mediated immunity is an immune response that does not involve antibodies, but rather involves the activation of phagocytes, natural killer cells (NK), antigen-specific cytotoxic T-lymphocytes, and the release of various cytokines in response to an antigen.
  • Cytotoxic T cells cause death by apoptosis without using cytokines.
  • Type IV hypersensitivity is often called delayed type hypersensitivity as the reaction takes two to three days to develop.
  • A classic example of delayed type IV hypersensitivity is the Mantoux tuberculin test in which skin induration indicates exposure to tuberculosis.

• Types of Adaptive Immunity

  • Cell mediated immunity is controlled by type 1 helper T-cells (Th1) and cytotoxic T-cells.
  • Helper-T cells facilitate the immune response by guiding cytotoxic T-cells to pathogens or pathogen-infected cells, while the cytotoxic T-cells will kill the pathogens or pathogen-infected cells.
  • Some of the ways in which cytotoxic T-cells kill pathogens include the release of granules that contain the cytotoxins perforin and granzyme, which lyse small pores in the membrane of a pathogen.
  • Helper-T cells will secrete cytokines, such as interferon-gamma, which can activate cytotoxic T-cells and macrophages.
  • This process is the reason why memory B cells can cause hypersensitivity (allergy) formation, as circulating IgE from those memory cells will activate a rapid inflammatory and immune response.

• Overview of Adaptive Immunity

  • The antigen is presented to immature helper T cells and cytotoxic T cells through binding the MHC II (helper T) or MHC I (cytotoxic T) to T-cell receptors.
  • Helper T cells activate B cells, which proliferate and produce antibodies specific to the antigen, while cytotoxic T cells destroy pathogens that bear the antigen that was presented to them by the APCs.
  • Additionally, the memory cell function enables the development of hypersensitivity disorders, such as allergies and many chronic diseases (like multiple sclerosis or myasthenia gravis).
  • Antigen presentation stimulates T cells to become either "cytotoxic" CD8+ cells or "helper" CD4+ cells.
  • Cytotoxic cells directly attack other cells carrying certain foreign or abnormal molecules on their surfaces.

• Lymphoid Cells

  • Activated NK cells release cytotoxic (cell-killing) granules that contain perforin and granzyme, which can lyse cell membranes and induce apoptosis to kill infected or abnormal cells.
  • They present antigens to B cells, produce cytokines that guide cytotoxic T cells, and activate macrophages.
  • Cytotoxic T-cells (CD8s)- destroy pathogens associated with an antigen.
  • Cytoxic T-cells are also the reason for much of the damage in cell-mediated hypersensitivity, autoimmune disorders, and organ transplant rejection.

• Complete Antigens and Haptens

  • A well-known example of a hapten is urushiol, which is the toxin found in poison ivy, a common cause of cell-mediated contact dermatitis, which is type IV hypersensitivity.
  • Usually, the first exposure causes only sensitization, in which there is a proliferation of helper and cytotoxic T-cells.

• Systemic Lupus Erythematosus

  • It is a Type III hypersensitivity reaction caused by antibody-immune complex formation.
  • Certain types of lupus nephritis, such as diffuse proliferative glomerulonephritis, require bouts of cytotoxic drugs.

• Hypersensitivities

  • Hypersensitivities are maladaptive immune reactions against harmless antigens (allergies) or against self antigens (autoimmunity).
  • The types of hypersensitivities include immediate, delayed, and autoimmunity hypersensitivities.
  • A large proportion of the population is affected by one or more types of hypersensitivity.
  • This type of hypersensitivity involves the TH1 cytokine-mediated inflammatory response.
  • Delayed hypersensitivity occurs in some individuals in response to contact with certain types of jewelry or cosmetics.

• Allergies

  • An allergy is a hypersensitivity disorder of the immune system.
  • Allergy is one of four forms of hypersensitivity and is formally called type I (or immediate) hypersensitivity.
  • If an immuno-response is seen, it can be concluded that the patient has a hypersensitivity (or allergy) to that allergen.