An immunologist has said that with some prompting, the protein STING can turn down the immune response or even block its attack on healthy body constituents like collagen, insulin and the protective covering of neurons – targets of the debilitating diseases.

Medical College of Georgia researchers saw STING’s critical role play out after they injected into the bloodstream submicroscopic DNA nanoparticles, engineered carriers for delivering drugs or genes into cells.

They learned that the magic is in STING, which recognizes the molecule that senses the DNA then prompts release of IDO, or indoleomine 2,3-dioxyegenase.

Dr. Andrew L. Mellor, immunologist at the Medical College of Georgia at Georgia Regents University said that the fact that STING is actually part of the DNA-sensing pathway tells us something we did not know before.

DNA nanoparticles apparently look to the body a lot like the debris that results when dying cells release DNA from their nucleus.

Researchers already knew there was a link between STING and immunity: the food-borne bacterium listeria releases cyclic dinucleotides to activate STING in cells it has infected.

When MCG researchers put the STING stimulus into the bloodstream, it results in suppression. Other scientists have generated the exact opposite effect by injecting STING stimulating reagents under the skin.

In the bloodstream, there are a lot of immune cells called phagocytes that ingest the submicroscopic particles that wind up in the fluid portion of the cell, called the cytoplasm, where most cellular activity happens.

There, sensors detect the DNA and trigger signaling that leads to expression of IDO. In this complex interplay, STING appears essential to recognizing the molecule that recognizes the DNA.

The study has been published in the Journal of Immunology.