Now scientists from the Florida campus of The Scripps Research Institute (TSRI) have identified a normally small subset of immune cells that may play a major role in the development of Crohn’s disease generally and in disease-associated steroid resistance specifically.
The study, published this week in an advance, online edition of the Journal of Experimental Medicine, focused on Th17 cells, part of a family of white blood cells that have been implicated in numerous autoimmune diseases, including Crohn’s disease.
In the new study, the researchers found that a subset of TH17 cells in humans expresses the multidrug transporter MDR1 and that these cells are linked to inflammation in Crohn’s patients. MDR1—a protein famous for promoting drug-resistance in tumors—may also act as a survival and steroid resistance factor in T cells, particularly in harsh environments such as the inflamed gut mucosa of Crohn’s disease patients.
“Our study is the first to identify and characterize this uniquely pro-inflammatory T-cell subset,” said biologist Mark Sundrud, a TSRI assistant professor who led the study. “We were able to sort these cells directly out of damaged tissue resected from Crohn’s patients and found that these pro-inflammatory cells are over-expressing genes that contribute to disease.”
Within healthy individuals, only approximately 5 to 10 percent of CD4+ T cells are MDR1-expressing TH17 cells. In contrast, the study found that of the CD4+ T cells found in actively inflamed tissue taken from Crohn’s patients, nearly 60 percent were MDR1+ TH17 cells.
The study also showed that these cells are resistant to both natural and synthetic steroids, a class of drugs considered a first-line defense against most autoimmune diseases.
“If a T cell expresses MDR1, it is likely to have an unfair growth advantage over surrounding T cells,” Sundrud said. “When exposed to steroids, it’s this subset of cells that will survive and thrive.”
Although it is unclear whether these pro-inflammatory cells become more prominent in patients over time, these findings suggest that steroid treatment itself may be directly responsible for the accumulation of these cells in Crohn’s patients. Sundrud and his colleagues continue to investigate.
The first author of the study, “Pro-Inflammatory Human Th17 Cells Selectively Express P-Glycoprotein and are Refractory to Glucocorticoids,” is Radha Ramesh of Tempero Pharmaceuticals. Other authors include Lina Kozhaya and Derya Unumaz of New York University; Kelly McKevitt of TSRI; Ivana M. Djuretic and Thaddeus J. Carlson of Tempero Pharmaceuticals; Maria A. Quintero, Jacob L. McCauley and Maria T. Abreu of the University of Miami. See http://jem.rupress.org/content/early/2013/12/30/jem.20130301.full
The study was supported by the National Institutes of Health (Grants R01AI065303, R21AI087973 and 1R01CA137869), Crohn’s and Colitis Foundation of America and The Micky & Madeleine Arison Family Foundation Crohn’s & Colitis Discovery Laboratory at the University of Miami.
About The Scripps Research Institute
The Scripps Research Institute (TSRI) is one of the world’s largest independent, not-for-profit organizations focusing on research in the biomedical sciences. TSRI is internationally recognized for its contributions to science and health, including its role in laying the foundation for new treatments for cancer, rheumatoid arthritis, hemophilia, and other diseases. An institution that evolved from the Scripps Metabolic Clinic founded by philanthropist Ellen Browning Scripps in 1924, the institute now employs about 3,000 people on its campuses in La Jolla, CA, and Jupiter, FL, where its renowned scientists—including three Nobel laureates—work toward their next discoveries. The institute’s graduate program, which awards PhD degrees in biology and chemistry, ranks among the top ten of its kind in the nation. For more information, see www.scripps.edu.
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