Dendritic cells present neuromuscular blocking agent‐related epitopes to T cells from allergic patients

Abstract

Anaphylactic reactions to neuromuscular blocking agents (NMBA) remain a major life-threatening and unpredictable complication during anaesthesia (1). Dendritic cells (DC) are considered to be the most powerful antigen-presenting cells (2). They can skew CD4+ T-cell differentiation towards a Th2 cytokine secretion pattern, which induces humoral responses dominated by an enhanced IgE production such as in allergic diseases. We undertook a case–control study to assess whether DC from patients having presented an anaphylactic reaction to an NMBA during anaesthesia were able to present the incriminated drug and to stimulate T cells. Ten patients sensitized to an NMBA and eight control subjects were involved in the study (Table 1). Monocytes and T lymphocytes were purified from fresh heparinized blood. Monocyte-derived DC (3) were generated in a 5-day culture with GM-CSF and IL-4, then matured for 2 additional days with TNF-α and PGE2 in the presence or absence of NMBA. Both NMBA-pulsed and control DC were co-cultured (ratio 1 : 10) with T lymphocytes from the same donor. After 5 days, proliferative responses were quantified by the mean [3H]-thymidine incorporation. Stimulation indices (SI) were calculated as ‘cpm in coculture with NMBA-pulsed DC/cpm in coculture with unpulsed DC’ and were considered as positive when SI > 2. In addition, lymphocyte transformation tests (LTT) were performed in the presence of the incriminated NMBA for each patient and in the presence of succinylcholine for healthy donors. No proliferative response was observed using LTT either in patients or in healthy donors. In contrast, NMBA-pulsed DC induced a significant proliferative response of T cells in two patients sensitized to succinylcholine and in one patient sensitized to atracurium. These specific responses demonstrate for the first time the capacity of DC to present NMBA-related epitopes that are recognized by T cells. Several mechanisms could explain how DC might process and present the incriminated NMBA (4). The drug might undergo covalent binding to soluble proteins processed by DC and consequently modified peptide might be expressed in association with MHC molecules. Another possibility is a covalent or noncovalent interaction of NMBA with the MHC–peptide complex directly at the surface of the DC. Nevertheless, experimental conditions for optimal NMBA presentation by DC remain to be defined, and this could be of particular importance for the development of DC-based assays for the characterization of NMBA-specific T-cell clones and for the in vitro diagnosis of an allergy to these drugs. This work was supported in part by a grant from the Société française d'Anesthésie et de Réanimation, France.