Hemophagocytes are a key characteristic of MAS. While it’s been known that they are present in MAS patients, their role has been unclear. Doctors aren’t sure if they are causing the disease or helping fight inflammation. Dr. Behrens says his research has turned up a clue in this debate because the mice in his animal model have all the features and characteristics of MAS, but they don’t have hemophagocytes.

“One of the things we see in MAS is your white blood cells drop, red blood cells drop and platelets drop. One theory is hemophagoctyes are eating those cells. But if I’m not seeing those hemophagocytes in the mice, I still see those cells drop,” Dr. Behrens says. “We have hypothesized they are involved in MAS but as a good guy. I think they might be involved in MAS but I think they are trying to help out. I think they are there to suppress disease.”

Dr. Behrens says this is the first time anyone has shown that the hemophagocyte can be separate and distinct from the disease process.

“They really are separate and I think we now have to change the way we think about that cell type,” he says. “That has implications for therapy because some of the therapies we use are to try to get rid of hemophagocytes.”

Treatments On the Horizon

He says the third major discovery is that the inflammatory molecule interferon gamma is a critical cytokine for MAS. Much like blocking the molecule tumor necrosis factor-alpha, or TNF-alpha, helps to treat patients with rheumatoid arthritis, if Dr. Behrens blocks interferon gamma in MAS, mice improve.

“That suggests if we could come up with a drug and there are potential drugs out there to block interferon gamma, that should work in patients with MAS,” Dr. Behrens says.

While he acknowledges that it takes a while to translate findings in mice to human patients, he says, he’s just getting started with this animal model and he knows it will help patients down the line.  

“We’re looking at years away for changes in practice because of something I do in mice. But it’s a first step,” Dr. Behrens says.

And it represents progress for patients like Hayley O’Keefe who wouldn’t be alive without Dr. Behrens’s research.

“This work has been successful,” Dr. Behrens says. “This would not have happened if I had not had Arthritis Foundation support.”