CD39+ regulatory T cells modulate the immune response to carbamazepine in HLA-B*15:02 carriers.

ABSTRACT

The HLA-B*1502 allele is associated with an increased risk of developing carbamazepine (CBZ)-induced Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN). Many studies, however, have demonstrated that a large majority of HLA-B*1502 individuals are unlikely to develop the adverse drug reaction while on CBZ. This phenomenon suggests that other factors that modulate the allergic immune response, such as regulatory T cells (Tregs), might contribute to an uncontrolled immune response in SJS/TEN. Peripheral blood mononuclear cells (PBMCs) from 15 healthy HLA-B*1502 carriers were isolated to investigate the role of Tregs in controlling the immune response towards CBZ. Recognition of CBZ was assessed using enzyme linked immunosorbent spot (ELISPOT) assay for IFN-γ, and the donor T-cell profiles were quantified by flow cytometry to differentiate CBZ responders from non-responders. As CD39 expression on Tregs promotes immune tolerance, we investigated the mechanisms of Treg suppression using inhibitors targeting the CD39/adenosinergic pathway. PBMCs from seven donors (responders) produced high levels of IFN-γ when re-exposed to CBZ, while eight donors (non-responders) did not. Flow cytometric analysis revealed that non-responders produced significantly higher frequencies of CD4+CD25+CD127loCD39+FoxP3+ Tregs compared to responders. CD39 inhibition using POM-1 inhibitor converted five of the eight non-responders into responders (P < 0.05). Higher frequencies of CD4+CD25+CD127loCD39+FoxP3+ Tregs was correlated with lower production of IFN-γ (P < 0.01). Our data suggest that CD4+CD25+CD127loCD39+FoxP3+ Tregs may play a role in promoting CBZ tolerance in HLA-B*1502 carriers. The CD39/adenosinergic axis can be a potential target to alleviate the uncontrolled immune response during this adverse drug event.