Voluntary activation of the sympathetic nervous system via breathing techniques can attenuate the innate immune response in humans.

“However, there's a human study that I definitely want to point out to you, because it was published more recently than the McEwen work. It was published in the Proceedings of the National Academy of Sciences for the USA, because there are Proceedings of the National Academy of Sciences for many other countries as well. The title of the paper is "Voluntary activation of the sympathetic nervous system." That's the system that causes fight or flight AKA stress, and causes release of adrenaline. "And attenuation of the innate immune response in humans." This is Kox et al. PNAS, Proceedings to the National Academy of sciences, 2014.”