type IV hypersensitivity
(noun)
A cell-mediated immune response that takes two to three days to develop.
Examples of type IV hypersensitivity in the following topics:
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Type IV (Delayed Cell-Mediated) Reactions
- Type IV hypersensitivity reactions are cell-mediated and take 2 to 3 days to develop.
- Type IV hypersensitivity is often called delayed type hypersensitivity as the reaction takes two to three days to develop.
- Unlike the other types, it is not antibody mediated but rather is a type of cell-mediated response.
- A classic example of delayed type IV hypersensitivity is the Mantoux tuberculin test in which skin induration indicates exposure to tuberculosis.
- Describe Type IV cell-mediated reactions and explain why they take two to three days to develop
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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.
- Below are some examples of Type II hypersensitivity-like autoimmunity.
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Type III (Immune Complex) Reactions
- Type III hypersensitivity occurs when there is little antibody and an excess of antigen, leading to the formation of small immune complexes.
- It is characterized by solvent antigens that are not bound to cell surfaces (which is the case in type II hypersensitivity).
- Hence, vasculitis, glomerulonephritis and arthritis are commonly-associated conditions as a result of type III hypersensitivity responses.
- Skin response to a hypersensitivity of this type is referred to as an Arthus reaction, and is characterized by local erythema and some induration.
- This is the third form of hypersensitivity in the Gell-Coombs classification, called Type III hypersensitivity.
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Type I (Anaphylactic) Reactions
- Type I (or immediate/anaphylactic) hypersensitivity can be caused by the body's response to a foreign substance.
- Type I hypersensitivity is also known as immediate or anaphylactic hypersensitivity.
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Immune Complex Autoimmune Reactions
- This is the third form of hypersensitivity in the Gell-Coombs classification, called Type III hypersensitivity.
- In immunology, the Arthus reaction is a type of local type III hypersensitivity reaction.
- Type III hypersensitivity reactions are immune complex-mediated.
- Typical of most mechanisms of the type III hypersensitivity, Arthus manifests as local vasculitis due to deposition of IgG-based immune complexes in dermal blood vessels.
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Type III and Type IV Secretion
- Type III and IV secretion systems are utilized by pathogenic bacteria to transfer molecules from the bacterial cell to the host cell.
- Specifically, Type III and Type IV secretion systems are utilized by gram-negative pathogenic bacteria to transport proteins that function as pathogenic components.
- The type IV secretion systems can either secrete or receive molecules.
- The type IV secretion system utilizes a process similar to this.
- An example of a pathogenic bacteria that utilizes the type IV secretion system is Helicobacter pylori.
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Synthetic Antimicrobial Drugs
- The history of antimicrobials begins with the observations of Pasteur and Joubert, who discovered that one type of bacteria could prevent the growth of another.
- It is important to make a distinction between sulfa drugs and other sulfur-containing drugs and additives, such as sulfates and sulfites, which are chemically unrelated to the sulfonamide group and do not cause the same hypersensitivity reactions seen in the sulfonamides.
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Rheumatic Fever
- This cross-reactivity is a Type II hypersensitivity reaction and is termed molecular mimicry.
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Viral Identification
- The genetic material within virus particles varies considerably between different types of viruses.
- An example of the first type is HIV, which is a retrovirus.
- Examples of the second type are the Hepadnaviridae, which includes Hepatitis B virus.
- Reoviruses)IV: (+)ssRNA viruses (+)sense RNA (e.g.
- An example of Baltimore Virus classification I: dsDNA virusesII: ssDNA virusesIII: dsRNA virusesIV: (+)ssRNA virusesV: (−)ssRNA virusesVI: ssRNA-RT virusesVII: dsDNA-RT viruses
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Primary Immunodeficiency Diseases
- The precise symptoms of a primary immunodeficiency depend on the type of defect.
- Tthe three most important types of antibodies are IgG, IgA and IgM.
- Tests for T cell function: skin tests for delayed-type hypersensitivity, cell responses to mitogens and allogeneic cells, cytokine production by cells
- The main members are various types of severe combined immunodeficiency (SCID).
- Immunodeficiency with hypopigmentation or albinism; for example, Chediak-Higashi syndrome, Griscelli syndrome type two