White blood cells have long reigned as the heroes of the immune system. When an infection strikes, the cells, produced in bone marrow, race through the blood to fight off the pathogen. But new research is emerging that individual organs can also play a role in immune system defense, essentially being their own hero. In a study examining a rare and deadly brain infection, scientists have found that the brain cells of healthy people likely produce their own immune system molecules, demonstrating an "intrinsic immunity" that is crucial for stopping an infection.