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Risk Variant of Autoimmune Disease Gene May Lead To New Treatment Options

Juvenile Arthritis Unaffected by MMR Vaccination
While children with juvenile arthritis have poor immunity, a new study finds that MMR booster shots can protect them from disease without worsening their arthritis. Joints | chambersclinic Flickr

A University of Minnesota Center for Immunology study published in the journal Immunity has opened new lines of investigation into how a gene called PTPN22 could assist in anti-inflammatory processes and fighting infections.

Researchers at the University of Minnesota discovered a decade ago that the variant form of the PTPN22 gene increased the risk of a person developing autoimmune diseases.

"[W]e have lacked a deep understanding how the variant creates that increased risk," said Dr. Erik Peterson, one of the study's lead authors. "We wanted to understand the molecular basis for PTPN22 association with disease."

Autoimmune diseases typically cause an inappropriate immune response to the body's own healthy cells and tissues. Rheumatoid arthritis, eczema, and Chrohn's disease are all types of autoimmune disorders.

The study focused on the role of myeloid cells in the immune system. They are one of the body's "first responders" when a virus or bacterium enters the system, producing chemicals that trigger inflammation to fight the infection. "We were intrigued by the idea that PTPN22 and its disease-associated variant might have a role in myeloid cell functions," Yaya Wang, a research associate in the University of Michigan Center for Immunology, said.

Both mouse and human myeloid cells carrying the risk variant of PTPN22 had decreased production of type 1 Interferons — molecules that boost immune responses to infections. The study found that mice lacking the PTPN22 gene had a decreased ability to fight infections, which correlated with reduced production of type 1 Interferon.

"Unexpectedly, we also found that PTPN22 suppresses inflammation," Wang said. "Furthermore, we showed that the PTPN22 risk variant is defective in suppressing inflammatory arthritis."

Peterson hopes that the research will help boost the drive to improve treatments and cures for autoimmune diseases.

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