Indicate whether each statement is true or false. If the statement is false, change the underlined word or phrase to make the statement true.
______ The tuberculin reaction is a type I hypersensitivity.

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Understand the classification of hypersensitivity reactions. There are four main types: Type I (immediate, IgE-mediated), Type II (antibody-mediated cytotoxic), Type III (immune complex-mediated), and Type IV (delayed-type, T-cell mediated).

Recall that the tuberculin reaction is a classic example of a delayed hypersensitivity reaction, which involves T-cell mediated immune responses rather than antibody-mediated responses.

Identify that the tuberculin reaction corresponds to a Type IV hypersensitivity, not Type I.

Since the statement says 'The tuberculin reaction is a type I hypersensitivity,' and this is incorrect, replace 'type I' with 'type IV' to make the statement true.

Thus, the corrected statement should read: 'The tuberculin reaction is a type IV hypersensitivity.'

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Types of Hypersensitivity Reactions

Hypersensitivity reactions are immune responses that cause tissue damage and are classified into four types (I-IV). Type I involves immediate allergic reactions mediated by IgE antibodies, while other types involve different immune mechanisms. Understanding these types helps identify the correct classification of immune responses like the tuberculin reaction.

Tuberculin Reaction

The tuberculin reaction is a diagnostic skin test used to detect prior exposure to Mycobacterium tuberculosis. It involves a delayed hypersensitivity response characterized by localized inflammation occurring 48-72 hours after antigen exposure, indicating a cell-mediated immune response rather than an immediate antibody-mediated one.

Delayed-Type Hypersensitivity (Type IV)

Delayed-type hypersensitivity (Type IV) is a T-cell mediated immune response that occurs hours to days after antigen exposure. It involves activation of sensitized T lymphocytes and macrophages, leading to inflammation and tissue damage, as seen in the tuberculin skin test, distinguishing it from immediate hypersensitivity reactions.

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