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One of the prime jobs of specialized immune cells, in most of the tissues in the body, is to engulf the billions of dead cells that are generated every day. When these garbage disposals stop doing their job, dead cells and their waste products rapidly pile up, destroying healthy tissues. The condition also leads to autoimmune diseases such as lupus and rheumatoid arthritis. 

Now researchers have discovered how two critical receptors on these garbage-eating cells identify and engulf dead cells in very different environments, according to a new study.

"To target these receptors as treatments for autoimmune disease and cancer, it's important to know exactly which receptor is doing what. And this discovery tells us that," said senior author of the work Greg Lemke, Salk professor of molecular neurobiology and the holder of Salk's Françoise Gilot-Salk Chair, in the press release.

The garbage disposing cells, known as macrophages, has an array of receptors on their surface, two of which, namely Mer and Axl, are responsible for recognizing dead cells in normal environments and inflamed environments, respectively.

"We thought Axl and Mer were doing the same job, and they are: they both recognize a so-called 'eat me' signal displayed on the surface of dead cells. But it turns out that they work in very different settings," said Lemke, whose lab first discovered the two receptors-which, along with a third, make up the TAM family-two decades ago.

"This basic research focus allowed us to discover a completely new aspect of immune regulation that no one-including any immunologist-had known about before," added Lemke.

Researchers are now looking into each receptor's activity in more detail. 

The study is published in the journal Nature Immunology.