Like a parasite exploiting its host, some tumors protect themselves by recruiting non-tumor cells that normally help keep the immune system in check, say researchers at the Medical College of Georgia. When the researchers looked into the lymph nodes where tumors drain – typically the first place tumors spread – they found a subset of normal host immune cells were expressing IDO, an immunosuppressive enzyme also expressed by the fetus to help avoid rejection by the mother’s immune system. They also found that when they gave a drug to block IDO expression, the immune system rallied. “Our hypothesis in this situation was that the bad guys in this case were actually cells from the host, perfectly normal cells that had, in a sense, been requested by the tumor,” says Dr. David Munn, pediatric hematologist-oncologist and lead author on the study published in the July 15 issue of Journal of Clinical Investigation.
