Effect of immune responses on breath methane dynamics.

Methane (CH) which can be detected in human breath has long been exclusively associated with anaerobic microbial activity (methanogenesis) in the gastrointestinal tract. However, recent studies challenge this understanding by revealing that CHmight also be produced endogenously in cells through oxidative-reductive stress reactions. Consequently, variations in breath CHlevels compared to an individual's baseline level might indicate enhanced oxidative stress levels, and, therefore, monitoring breath CHlevels might offer great potential for '' diagnostics such as disease diagnosis, monitoring the efficacy of treatments, or during the application of personalized medicine. To evaluate the effects from immune responses triggered by infections, inflammations, and induced perturbation by vaccination on CHdynamics in breath, two subjects were monitored over a period of almost 2 years. Breath CHlevels were measured by gas chromatography equipped with a flame-ionization detector. Both subjects exhibited significant deviations (positive and negative, respectively) from their normal CHbreath levels during periods of potential enhanced immune activity. Deviations from the 'healthy state' were indicated by the exceeding of individual CHranges. Moreover, for the first time we could clearly prove CHdegradation induced through vaccination by measuring stable carbon isotopes of CHusing gas chromatograph-combustion-isotope ratio mass spectrometry. Hence, breath CHconcentration and isotopic analyses may be used as a biomarker to evaluate specific immune responses and individual immune states.