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Researchers discover malaria switch cells

13 May 2009

Professor Magdalena Plebanski

Scientists have determined that a subset of immune cells may cause malaria patients to contract the severe form of the disease.

Led by Monash immunologist Professor Magdalena Plebanski of the Vaccine and Infectious Diseases Laboratory, the international team found that patients with the severe form of malaria have a specific type of cell in their body that people with the uncomplicated disease do not.

This type of cell turns off the immune system and can allow the parasite to grow uncontrollably.

The team investigated the relationship between regulatory T (Treg) cells, parasite burden, and disease severity in adult malaria patients with either uncomplicated or severe malaria.

They identified elevated levels of a new highly-suppressive subset of Treg cells in those patients with severe malaria.

"Regulatory T cells are a small, specialised subset of immune cells that suppress the activation and expansion of effector immune cells, which partake in parasite elimination," Professor Plebanski said.

"The Treg cell subset associated with severe disease in humans expresses a unique combination of surface markers.

"Our results indicate that severe malaria is accompanied by the induction of highly-suppressive Treg cells that can promote parasite growth and as such we caution against the induction of these Treg cells when developing effective malaria vaccines."

It is estimated that 500 million people live in malaria risk areas. The severe form causes death in one to three million people each year.

Until now the bodily factors that enable some patients to survive the disease, while other patients contract the severe form and sometimes die, has been largely unknown.

"Targeting this cell type may lead to new medicines to fight malaria. Further studies are needed to determine if this new cell is promoting severe forms of other inflammatory diseases," Professor Plebanski said.