Scientists believe the research, in mice, has important implications for treating malignant and deadly skin cancer.
Mice with melanoma were treated with white blood cells that produce the molecule, interleukin-9 and the animals showed a “profound” resistance to tumour growth.
Interleukin-9 is a “cytokine”, a type of cell-signalling molecule, and the cells that produce it, called TH9 cells, have been found in both normal human blood and skin.
But they are either absent or present at very low levels in human melanoma tissue.
The new research is reported in the latest issue of the journal Nature Medicine.
Lead scientist Dr Thomas Kupper, from Brigham and Women’s Hospital in Boston, US, said: “Immunotherapy of cancer is coming of age, and there have been exciting recent results.”