Resolving a decade of debate, scientists claim to have distinguished two cell messengers -- one causing cell suicide, the other inflammation.
An international team, led by Walter and Eliza Hall Institute, has identified the form of a molecular messenger called Fas ligand, which is responsible for killing cells during programmed cell death -- also called apoptosis.
Apoptosis is an important process in human biology as it removes unwanted and dangerous cells from our bodies, protecting us against cancer development and diseases where the immune system attacks the body's own tissues, such as in lupus or insulin-dependent diabetes.
This cell death process can be activated by proteins on the surface of cells. The most prominent of these cell surface proteins is Fas ligand, which exists in two forms -- membrane-bound or secreted -- and binds to a surface receptor called Fas.
"There has been a lot of debate among the scientific community over which of the forms causes cell death but also which of the forms may induce an inflammatory response.
"What we have shown is that it is the membrane-bound Fas ligand that is essential for cell death and is therefore the body's guardian against lymphadenopathy (the swelling of lymph nodes), autoimmunity and cancer," team leader Professor Andreas Strasser said.
The findings, published in the Nature journal, also demonstrated that although secreted Fas ligand does not have a role in cell killing, too much secreted Fas can promote tumour development and autoimmunity.
"In certain autoimmune conditions and types of lymphoma/leukaemia there is massive over-production of secreted Fas ligand.
"Since our research shows that secreted Fas is pro-inflammatory, and therefore detrimental, and since the aforementioned disease states are characterised by inflammatory tissue destruction, it may be possible to alleviate some of the manifestations of these diseases by neutralising the secreted Fas ligand with antibodies or soluble receptors," Prof Strasser said.