A study has shown that T cell receptors are able to switch their conformation from an inactive to an active state spontaneously without any antigens present, biologists from the University Freiburg announced on Friday.

Previously, however, researchers tend to believe that an antigen like a pathogen must bind to a T cell receptor, which is an important part of the human immune system, in order to activate it, thereby triggering an immune response.

"We demonstrated that it's not the binding to an antigen that causes the switch in the conformation; it happens spontaneously," said Wolfgang Schamel from the University Freiburg.

Biologists from the university discovered that cholesterol prevents an immune response even when no antigen is present. Cholesterol binds and stabilizes inactive receptors, giving it a decisive role in the activation of a T cell.

Because only cholesterol can bind to an inactive T cell receptor, this is a specific interaction, said the study that has been published recently in the journal Immunity.

"We are among the first researchers to be able to demonstrate a functional effect of an interaction of a lipid with a transmembrane protein," said Schamel, adding that the interaction regulates the conformation and hence the activity of the receptor.