"Chaotic Arrhythmia" During Successful Resuscitation After Ingestion of Yew (Taxus baccata) Needles.

OBJECTIVE: The study aims to describe the management of a case of life-threatening yew (Taxus baccata) intoxication. BACKGROUND: The needles of the yew tree contain highly cardiotoxic taxines. Intoxication with taxines, typically as part of suicide attempts, may lead to potentially lethal arrhythmias which often require prolonged cardiopulmonary resuscitation and other supportive measures. No specific therapy has been described. In some cases, extracorporeal life support has been used. CASE: After an attempted suicide with yew needles and out-of-hospital cardiac arrest, a female adolescent was resuscitated for 6 hours according to Advanced Cardiovascular Life Support guidelines. Complex ventricular tachycardias were treated by repeated direct current shocks and broad complex bradycardia managed with transvenous cardiac pacing. Antiarrhythmic drugs (amiodarone, lidocaine), magnesium sulfate, and supportive measures (intravenous lipids, sodium bicarbonate) were provided. The arrhythmias finally resolved, and the patient did not show any significant neurological or cardiac short-term sequelae after 24 hours. RESULTS: The authors describe the successful management of a case of severe taxine intoxication by prolonged conventional advanced cardiac life support lasting for more than 6 hours. CONCLUSIONS: In life-threatening yew intoxication, prolonged cardiopulmonary resuscitation is absolutely essential owing to the long duration of the cardiotoxic action of taxines and can lead to an outcome without cardiac or neurological sequelae.

Natural variations at position 93 of the invariant Vα24-Jα18 α chain of human iNKT-cell TCRs strongly impact on CD1d binding.

Human invariant natural killer T (NKT) cell TCRs bind to CD1d via an "invariant" Vα24-Jα18 chain (iNKTα) paired to semi-invariant Vß11 chains (iNKTß). Single-amino acid variations at position 93 (p93) of iNKTα, immediately upstream of the "invariant" CDR3α region, have been reported in a substantial proportion of human iNKT-cell clones (4-30%). Although p93, a serine in most human iNKT-cell TCRs, makes no contact with CD1d, it could affect CD1d binding by altering the conformation of the crucial CDR3α loop. By generating recombinant refolded iNKT-cell TCRs, we show that natural single-nucleotide variations in iNKTα, translating to serine, threonine, asparagine or isoleucine at p93, exert a powerful effect on CD1d binding, with up to 28-fold differences in affinity between these variants. This effect was observed with CD1d loaded with either the artificial α-galactosylceramide antigens KRN7000 or OCH, or the endogenous glycolipid ß-galactosylceramide, and its importance for autoreactive recognition of endogenous lipids was demonstrated by the binding of variant iNKT-cell TCR tetramers to cell surface expressed CD1d. The serine-containing variant showed the strongest CD1d binding, offering an explanation for its predominance in vivo. Complementary molecular dynamics modeling studies were consistent with an impact of p93 on the conformation of the CDR3α loop.