Cytotoxic‑based assays in delayed drug hypersensitivity reactions induced by antiepileptic drugs

Introduction Cytotoxic mechanisms are present in the majority of delayed drug hypersensitivity

reactions, but are not used as a diagnostic tool.

Objectives The aim of the study was to compare cytotoxic‑based assays with a proliferation assay

and drug patch tests in patients with maculopapular eruptions induced by antiepileptic drugs.

Patient s and methods Peripheral blood mononuclear cells of 23 patients and 24 controls exposed to

the drugs were cultured under defined conditions. A drug‑specific response was assessed by measuring

granzyme B (GrB) release with an enzyme‑linked immunospot assay, intracellular expression of granulysin

(Grl) in CD3–NKp46+ cells with flow cytometry, perforin concentrations in cell culture supernatants with

an enzyme‑linked immunosorbent assay, and using the lymphocyte proliferation test. Patch tests with

culprit drugs were done in all patients.

Result s Lymphocyte proliferation, GrB release, and Grl expression were significantly higher in patients

than in controls, while perforin concentrations were not elevated. The sensitivities were 30.4%, 55%,

39.1%, and 17.4% for proliferation, GrB, Grl, and perforin‑based assays, respectively. A significantly

higher rate of positive results was observed when assays were done within 2 years after a drug‑induced

reaction. The specificities of all assays remained in the range of 95.8% to 100%. The results of patch

tests were positive only in 3 patients (sensitivity, 14.3%) and negative in all controls.

Conclusions In vitro assays based on the detection of Grl, and in particular of GrB, are superior to

routine diagnostic tests in patients with hypersensitivity to antiepileptic drugs. They can detect a low‑level

response that might be overlooked by standard techniques. In the remission phase, drug‑specific cells

are more easily detectable directly in the circulation than in the skin.