Delayed-type hypersensitivity reaction (DTH)

Delayed-type hypersensitivity (DTH), or Type IV hypersensitivity, is a cell-mediated immune response that typically takes 24 to 72 hours to manifest following exposure to an antigen. Unlike other hypersensitivity types, DTH is not mediated by antibodies but by sensitized T-lymphocytes, particularly Th1 and Th17 subsets, which release cytokines like interferon-gamma (IFN-γ) and tumor necrosis factor-alpha (TNF-α) to activate macrophages and induce local inflammation (StatPearls, 2023). This reaction plays a dual role in human health; it is essential for defending against intracellular pathogens such as Mycobacterium tuberculosis, yet it is also the driving mechanism behind contact dermatitis, transplant rejection, and several autoimmune conditions (NIH, 2022). Therapeutic intervention often focuses on suppressing the various stages of this response using corticosteroids, calcineurin inhibitors, or biologics that neutralize specific cytokines or T-cell signaling pathways. Because DTH involves a complex cascade of cellular interactions rather than a single molecule, it is characterized as a physiological reaction or pathway rather than a singular therapeutic target (PubMed, 2021).

Other names

Type IV hypersensitivityCell-mediated hypersensitivityT-cell mediated hypersensitivityDelayed-type hypersensitivity

Inhibition of T-cell activation, suppression of cytokine release (IFN-gamma, TNF-alpha), calcineurin inhibition, and blockade of T-cell costimulation.