The full form of DTH in medical terms is Delayed-Type Hypersensitivity.
Delayed-Type Hypersensitivity (DTH) is a type of cell-mediated immune response that primarily involves T cells rather than antibodies. It is also called delayed-type hypersensitivity response. This means that the reaction to an antigen (a substance that triggers an immune response) doesn't happen immediately, but rather takes 24-72 hours to develop.
Here's a breakdown of key aspects of DTH:
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Cell-Mediated Immunity: DTH is a form of cell-mediated immunity, meaning that it relies on the action of specific immune cells (T cells), rather than antibodies produced by B cells.
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T Cell Involvement: The main players in DTH reactions are T helper cells (specifically Th1 cells) and cytotoxic T cells.
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Antigen Presentation: The process begins when antigen-presenting cells (APCs), such as macrophages or dendritic cells, engulf and process an antigen.
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T Cell Activation: The APCs then present the processed antigen to T helper cells, which become activated.
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Cytokine Production: Activated T helper cells release cytokines, such as interferon-gamma (IFN-γ), which recruit and activate other immune cells, including macrophages.
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Macrophage Activation: Activated macrophages contribute to inflammation and tissue damage at the site of antigen exposure.
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Delayed Reaction: The delayed nature of DTH is due to the time required for T cell activation, cytokine production, and recruitment of other immune cells to the site.
Examples of DTH Reactions:
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Tuberculin Skin Test (Mantoux Test): This test is used to detect previous exposure to Mycobacterium tuberculosis, the bacteria that causes tuberculosis. A small amount of tuberculin (a protein extract from the bacteria) is injected under the skin. A positive reaction, indicated by induration (a raised, hardened area), develops 48-72 hours later.
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Contact Dermatitis: Allergic contact dermatitis, such as poison ivy rash, is a type of DTH reaction. It occurs when the skin is exposed to an allergen, triggering a T cell-mediated immune response that results in inflammation, itching, and blistering.
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Granuloma Formation: In some chronic infections, DTH responses can lead to the formation of granulomas, which are clusters of immune cells that wall off the infection.
In summary, Delayed-Type Hypersensitivity (DTH) is a crucial part of the immune system's defense against various pathogens and substances.
