Establishment of T cell stimulation by flucloxacillin in HLA-B*5701+ flucloxacillin-naïve individuals (52.21)

Abstract

Rational: Drug induced liver injury (DILI) is a main cause of drug withdrawal. A particularly interesting example is flucloxacillin (FLUX)-DILI, which is associated with the HLA-B*5701 allele. To better understand this side effect, we established an in vitro model for FLUX induced T cell activation. Methods: Peripheral blood mononuclear cells from FLUX-naïve, HLA-B*5701+ healthy donors were induced by iterative in vitro restimulations with FLUX. FLUX-specific T cells (FLUX-Tc) were enriched by positive selection of CD107a expressing cells and characterized by flow cytometry and 51Cr-release assay. Results: FLUX-Tc are mainly CD8+. They react by IFNγ secretion and CD107a upregulation upon drug stimulation and are cytotoxic against autologous antigen presenting cells (APC). Cytotoxicity and reactivity was observed only if free FLUX was added to the system. FLUX-pulsed APC were not able to elicit a FLUX specific T cell response if FLUX was not additionally added. The direct addition of FLUX to FLUX-Tc resulted in their activation even in the absence of APC. This self-presentation and reactivation was still observed in the presence of the proteasome inhibitors lactacystin and bortezomib. Conclusion: The APC independent T cell reactivity and the non-involvement of the proteasome is best explained by a direct interaction of FLUX with the restricting HLA-B*5701 molecule. How and why this activation leads to a preferential damage of liver cells needs further investigation.