It is well known that music has a fundamental effect on humans - it can reduce stress, enhance relaxation, and provide a distraction from pain and therefore it is used clinically to reduce anxiety after heart attack, or to ease pain and nausea during bone marrow transplantation. Now, Japanese researchers have demonstrated that music can reduce rejection of heart transplants in mice by influencing the immune system. According to Science Daily, the researchers investigated if music could influence the survival of heart transplants in mice and found that opera and classical music both increased the time before the transplanted organs failed. However, that effect was not significant in mice exposed to single frequency monotones and new age music. Though the link between music and reduced rejection is not clearly understood yet, the team led by Dr Masanori Niimi pinpointed the source of this protection to the spleen. It was revealed that levels of some immune cells produced by the spleen were changed by listening to opera or classic music. Dr Uchiyama and Jin revealed, “Opera exposed mice had lower levels of interleukin-2 (IL-2) and interferon gamma (IFN-?). They also had increased levels of anti-inflammatory IL-4 and IL-10. Significantly these mice had increased numbers of CD4+CD25+ cells, which regulate the peripheral immune response.” It seems that music really does influence the immune system -- although the mechanism behind this still is not clear. Additionally, this study only looked at a limited selection of composers, so the effect of music on reducing organ rejection may not be limited to opera. The study was published in BioMed Central’s open access journal Journal of Cardiothoracic Surgery.