Scientists uncover drivers of recurrent arthritis after immunotherapy, suggesting potential biomarkers

by University of Texas MD Anderson Cancer Center

edited by Sadie Harley, reviewed by Alexander Pol

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A new study led by researchers at The University of Texas MD Anderson Cancer Center has shown that inflammatory arthritis occurring as a side effect of immune checkpoint inhibitors behaves like an immune-memory disease, suggesting that certain immune cell populations could serve as biomarkers or targets for therapies.

The study was co-led by UT MD Anderson researchers Roza I. Nurieva, Ph.D., professor of Immunology; Synat Keam, Ph.D., a postdoctoral fellow in the Nurieva Laboratory; and Yuanteng Jeff Li, M.D., assistant professor of General Internal Medicine, along with Sang Taek Kim, M.D., Ph.D., assistant professor at Yale University.

Published in Cancer Immunology Research, the findings showed that two specific immune cell populations were present in both initial and recurrent arthritis flares.

"Cancer immunotherapy works by creating a lasting immune response against tumors, but that same persistence may also contribute to recurring inflammatory side effects that can be debilitating for patients," Nurieva said. "By identifying the immune cells that drive recurrent arthritis, we can inform treatment strategies that reduce the risk of future flares while preserving the therapy's effectiveness against cancer."

Why does inflammatory arthritis develop after immunotherapy?

Immune checkpoint inhibitors are a common type of immunotherapy designed to activate the immune system to eliminate cancer cells. Sometimes, the immune system can also attack a patient's joints, causing a painful condition called inflammatory arthritis.

Roughly 20% to 50% of those patients experience this side effect more than once, and some continue to experience arthritis symptoms for months or years after treatment ends. Additionally, recurrent flares are often more severe than initial episodes, indicating an increasingly aggressive inflammatory response over time.

What did the researchers discover?

When researchers analyzed joint fluid collected from six patients during their first arthritis flare and a recurrent flare, they identified two specific immune cell populations that were present during both episodes: inflammatory CD8 T cells and a specialized group of CD4 T cells co-expressing PD-1 and CXCL13.

The persistence of these immune cell populations indicates that the immune system is reactivating previously established inflammatory cells rather than generating a completely new response each time.

Researchers also discovered that these cells produced higher levels of inflammatory signaling molecules during subsequent flares and appeared to return in a more activated state. Unexpectedly, regulatory T cells, which normally help suppress excessive immune responses, also produced inflammatory molecules in recurrent flares, potentially weakening one of the body's natural mechanisms for controlling inflammation.

The study found that inflammatory immune cells were linked through extensive networks of signaling molecules. These connections became more pronounced during the second flare, revealing a coordinated inflammatory environment within the joint rather than the activity of only a few isolated cell types.

What's next for this research?

Although inflammatory arthritis is a recognized side effect of immunotherapy, it remains unclear why it develops in some patients and not others.

Future research could explore whether these immune cell populations can serve as biomarkers to identify patients at the highest risk for future flares. The findings also provide a foundation for developing targeted therapies that suppress arthritis while preserving the beneficial effects of immunotherapy.

More information

Synat Keam et al, Immune hallmarks of recurrent immune checkpoint inhibitor-mediated inflammatory arthritis, Cancer Immunology Research (2026). DOI: 10.1158/2326-6066.cir-25-1639

Key medical concepts

Immune Checkpoint InhibitorsT-Lymphocytes, Regulatory

Clinical categories

RheumatologyOncologyAllergy and immunology Provided by University of Texas MD Anderson Cancer Center Who's behind this story?

Sadie Harley

BSc Life Sciences & Ecology. Microbiology lab background with pharmaceutical news experience in oil, gas, and renewable industries. Full profile →

Alexander Pol

PhD nano-engineering from Delft University. Published researcher and journal reviewer. Brings scientific insight to content standards. Full profile →

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