A few years ago there was a very simple view of the relationship between the immune system and cancer. Immune cells, such as natural killer cells, had the capacity to destroy cancer cells in the laboratory. So they must do so inside the body, surely? The development of cancer was blamed on a failure of the immune system's surveillance - a failure to spot microtumours and dispatch them before they could take root.
Complementary therapists seized on this idea, reasoning that if you could boost up the immune system with a beautiful thought, a massage or a potion then you could reduce your chances of getting cancer - or even help the immune system attack fully-developed tumours.
But now a far more complicated picture is emerging. It is not a simple case of cancer cells bad and immune cells good. We now know, for instance, that immune cells can sometimes help the cancer cells instead of attacking them.
Some recently-published research has demonstrated a new connection between cancer and immune cells. It has long been suspected that prolonged inflammation, for example in the stomach lining, might cause cancer but exact molecular mechanisms are hard to pin down. A team in Ohio has now discovered a link between immune cells, inflammation and a form of blood cancer. They were able to demonstrate this using a combination of mice and human leukaemia cells.
Immune cells communicate with other cells by releasing a range of chemicals, collectively know as cytokines or interleukins. One of these, known as Interleukin-15, is released during inflammation. Inflammation is useful as a short term measure but if it becomes long term, you have an excess of Interleukin-15 in circulation.
The team has demonstrated that an excess of Interleukin-15 can stimulate a type of immune cell known as a large granular lymphocyte (LGL) to become malignant giving rise to a rare form of leukaemia.
Not content with this breakthrough, they managed to "turn off the pathway" and reverse the process - curing the mice of their LGL leukaemia.
So here we have a double success - demonstration of a molecular pathway whereby an immune chemical associated with inflammation can cause a specific cancer - and reversing the process.
So if a complementary therapist tells you that something will “boost your immune system” proceed with caution. The immune system is not a simple device. It’s a vast collection of cells and complex chemicals, interacting in ways that we are only beginning to understand in detail.