Once a disease has entered the body, all parts which are healthy must fight it: not one alone, but all. Because a disease might mean their common death. Nature knows this; and Nature attacks the disease with whatever help she can muster.
With the modern diseases (once TB, now cancer) the romantic idea that the disease expresses the character is invariably extended to assert that the character causes the disease -- because it has not expressed itself. Passion moves inward, striking and blighting the deepest cellular recesses.