Which condition is a classical example of Type IV hypersensitivity?

Which condition is a classical example of Type IV hypersensitivity?

• A. Allergic rhinitis
• B. Graves' disease
• C. Contact dermatitis
• D. Myasthenia gravis

Answer: (C)

Type IV hypersensitivity is a T cell–mediated, delayed response. After sensitization, re-exposure activates T cells to release cytokines that recruit and activate macrophages, causing tissue inflammation, typically 24–72 hours later. Contact dermatitis is the classic example because it arises from a sensitized T-cell reaction in the skin to substances like nickel or poison ivy. In contrast, allergic rhinitis is driven by IgE antibodies (Type I hypersensitivity), while Graves' disease and myasthenia gravis involve autoantibodies causing tissue damage (Type II hypersensitivity). So the condition described aligns with a T cell–mediated, delayed-type response.

Type IV hypersensitivity is a T cell–mediated, delayed response. After sensitization, re-exposure activates T cells to release cytokines that recruit and activate macrophages, causing tissue inflammation, typically 24–72 hours later. Contact dermatitis is the classic example because it arises from a sensitized T-cell reaction in the skin to substances like nickel or poison ivy. In contrast, allergic rhinitis is driven by IgE antibodies (Type I hypersensitivity), while Graves' disease and myasthenia gravis involve autoantibodies causing tissue damage (Type II hypersensitivity). So the condition described aligns with a T cell–mediated, delayed-type response.