Exploiting differences Most current cancer treatments are like blunt sledgehammers. Differences are what the immune system is all about. Immune cells detect invading microbes based on the different proteins displayed on the microbes' surface, and those difference trigger mechanisms that destroy the invaders.
Cancer cells are also different from normal human cells.
For decades scientists have hoped that they could understand the molecular changes behind these differences, and exploit them to come up with more specific anti-cancer therapies. Cancer cells often move around. The idea of using the immune system as a more exact weapon has been around since 1893, when William Coley observed cancer regression after erysipelas infection. The infection, Coley presumed, had triggered the immune system to attack a protein that was similar on both microbe and cancer cell. Coley's experience was fortuitous, but, as molecular knowledge about cancer cells grew, scientists tried immunizing against cancer using specific proteins.