"Iceman" Wim Hof, who is well known for the several activities he has accomplished in low temperatures, believes that it is possible to control his immune response through concentration and meditation. Professor Peter Pickkers administered endotoxin, a component of bacteria that the immune system will react to as it gives "flu-like" symptoms, to Hof while he was meditating to see if his immune system would react. Hof's immune response was decreased by 50% compared to other healthy volunteers. Also, Hof barely showed any "flu-like" symptoms. Because these results have only been collected from one subject, several other people will have to be tested in order to confirm that this is possible.