The master regulators of delayed-type drug hypersensitivity reactions.

PURPOSE OF REVIEW: Delayed-type drug hypersensitivity reactions (DTHRs), ranging from benign exanthems to life-threatening severe cutaneous adverse reactions such as Stevens-Johnson syndrome/toxic epidermal necrolysis (SJS/TEN) and drug reaction with eosinophilia and systemic symptoms (DRESS), are mediated by drug-specific T cells and governed by complex regulatory networks. This review highlights recent advances in understanding the master regulators orchestrating DTHR pathogenesis.

RECENT FINDINGS: HLA-restricted T-cell activation is amplified by cytokine-driven loops, notably the tumor necrosis factor-α axis, which disrupts peripheral tolerance via VISTA inhibition and recruits effectors through CXCL10. The JAK-STAT pathway plays a pathogenic role across immune and stromal compartments. Beyond genetic risk, epigenetic modifications (e.g., DNA methylation) fine-tune immune reactivity. Emerging immunomodulatory circuits involving sensory neuropeptides (CGRP) and innate immune cells (NK cells, neutrophils) critically shape adaptive responses. Terminal epidermal damage involves convergent cell death pathways (apoptosis, ferroptosis, and necroptosis) often triggered by systemic exosomal signals.

SUMMARY: Deciphering these interconnected regulatory layers reveals novel diagnostic biomarkers and therapeutic targets, paving the way for precision medicine in DTHRs.