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The IFN-γ ELISpot assay could be a useful tool to identify culprit drugs in SCAR patients when culprit drug identification is urgently needed during the acute phase of drug allergy.

The measurement of oxypurinol/anti-PD-L1-inducing IFN-γ-releasing cells yields a high diagnostic value in distinguishing between allopurinol-allergic and control subjects. This technique is beneficial in confirming diagnosis of allopurinol-induced SCARs in patients whose reaction develops while taking multiple drugs.

Background: Stevens-Johnson syndrome/toxic epidermal necrolysis (SJS/TEN) and drug reactions with eosinophilia and systemic symptoms (DRESS) are both severe cutaneous adverse reactions. Keratinocyte death is much more prominent in SJS/ TEN compared to DRESS. Objective: This study aimed to investigate the role of exosomal miRNAs on keratinocyte death in SJS/TEN. Methods: Peripheral blood mononuclear cells (PBMCs) from SJS/TEN and DRESS patients were stimulated with the culprit drugs. The exosomes released in cell supernatants were co-incubated with HaCaT cells to study the cytotoxic effects on keratinocytes. Exosomal miRNA sequencing analysis was performed to compare the expression patterns between SJS/TEN and DRESS subjects. HaCaT cells were then transfected with miRNA mimics and inhibitors to explore the functions of miRNAs on keratinocyte cell death. Results: Cytotoxic effects of PBMC-derived exosomes on keratinocytes were demonstrated in SJS/TEN and could be neutralized with exosome inhibitors. Cytotoxic effects of PBMC-derived exosomes from SJS/TEN subjects were higher after incubating PBMCs with the culprit drugs than those incubating with irrelevant drugs and unstimulated controls. The sequencing data revealed differential expressions of 61 exosomal miRNAs between SJS/TEN and DRESS. Exosomal miR-4488 was upregulated while miR-486-5p, miR-96-5p and miR-132-3p were downregulated in SJS/TEN compared to DRESS as determined by quantitative real-time PCR. The increased percentage of apoptotic cells upon transfection of HaCat cells was 36.3% and 34.9% with miR-4488 mimic and miR-96-5p inhibitor, respectively. Conclusion: This study illustrated the regulatory functions of exosomal miRNAs in controlling keratinocyte death in SJS/TEN. Exosome inhibitors might have a therapeutic role in SJS/TEN.

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