The Norway scientists compared the immune systems of 24 mice living in the wild with 31 mice living under sterilized lab conditions. The wild mice had more killer cells which belong to the lymphocytes, a subgroup of the white blood cells without antigen-specific receptors, in their immune systems.
Because of this they are capable of responding differently and more quickly to tumor cells and potentially damaging pathogens. As humans do not grow up in a sterilized enviromnent their immune system is not comparable to lab mice. This should be considered if scientists want to develop new drugs for automimmune diseases, the researchers said. In many cases, new drugs are suitable for healing laboratory mice but not humans.
Source: http://www.sueddeutsche.de/