Researchers at the Wistar Institute said they have discovered seven different receptors on the outside of the body's immune system T cells that can "tamp down immune responses during a prolonged battle with an infectious pathogen or against developing cancer."

Assistant Professor E. John Wherry, the study's lead author, said the research also showed the seven receptors likely control different aspects of T cell responses, such as division or expansion and controlling viral replication.

"This amount of control over T cells' response is remarkable," he said. "It suggests that layers of negative regulation exist on exhausted T cells from coexpression of multiple inhibitory receptors. My bet is that these receptors inhibit different aspects of the T cells' response but that the net result of their activation is to turn specific T cell populations off.

"That suggests it may be possible to not only dramatically enhance anti-viral or anti-tumor T cell responses but also to fine tune which response you want to enhance in order to reverse T cell exhaustion and continue fighting an infection or disease."

The new research is reported online in the journal Nature Immunology.