What is the Difference Between Immediate and Delayed Hypersensitivity?

The main difference between immediate and delayed hypersensitivity lies in the timing of the reaction and the immune system components involved.

Immediate Hypersensitivity:

• Occurs within 24 hours of exposure to the antigen.
• Type I, II, and III hypersensitivity reactions are considered immediate hypersensitivity reactions.
• Mediated by IgE, IgM, and IgG antibodies.
• Examples include anaphylaxis, allergic rhinitis, and certain food allergies.

Delayed Hypersensitivity:

• Occurs more than 12 hours after exposure to the allergen, with a maximal reaction time between 48 and 72 hours.
• Type IV hypersensitivity reaction is considered a delayed hypersensitivity reaction.
• Mediated by T cells, macrophages, and CD8+ cells.
• Examples include contact dermatitis (e.g., poison ivy rash), tuberculin skin test reactions, granulomatous inflammation (e.g., sarcoidosis, Crohn's disease), allograft rejection, graft versus host disease, and autoimmune hypersensitivity reactions.

In summary, immediate hypersensitivity reactions are faster and mediated by antibodies, while delayed hypersensitivity reactions are slower and mediated by T cells and macrophages.

Comparative Table: Immediate vs Delayed Hypersensitivity

The main difference between immediate and delayed hypersensitivity lies in the time it takes for the reaction to occur and the cells involved in the immune response. Here is a comparison of the two types of hypersensitivity reactions:

In summary, immediate hypersensitivity reactions are faster and involve antibodies, while delayed hypersensitivity reactions are slower and involve T cells and macrophages.