Quality control mechanism `discovered`

Washington: Scientists have discovered what they claim is a "quality control" mechanism which ensures that the human immune system is effectively destroying harmful viruses and bacteria.

An international team, led by Monash University, has solved a 15-year puzzle by working out the structure and function of a protein called pre-T alpha that is essential in guiding the correct expression of various receptors expressed by T lymphocytes, white blood cells of the immune system.

These receptors, known as T cell receptors, recognize unique components of microbial pathogens.

Team leader Prof Jamie Rossjohn said understanding the structure of pre-T alpha explains a fundamental step in T cell development and anti-microbial immunity.

"We showed that the pre-T alpha molecule not only assists in the expression of functional T cell receptors but it also allows two molecules to bind together, which alerts the T cell that this receptor is constructed properly, allowing the T cell to move to the next step in its development," he said.

According to team member Prof Jim McCluskey from the University of Melbourne, without T cell receptors we would be profoundly immunodeficient and therefore pre-T alpha plays an essential role in ensuring proper immunity.

"Additionally, there is some evidence that pre-T alpha may also be involved in some childhood leukaemias, so this new knowledge of how it functions may be important in diagnosis and treatment of acute lymphoblastic leukaemia," he said.