MDR1 expression is found for about 5 to 10% of Th17 cells. In Crohn's disease this expression increases to about 60%. MDR1 Th17 cells are resistant to steroids and are implicated in autoimmune disease. If a patient with these cells is treated with steroids, they will give Th17 MDR1 cells the possibility to thrive, while other cells are influenced by the treatment. Steroids could make Crohn's disease worse, not only by promoting resistance to treatment but also by increasing the numbers of inflammatory cells. http://www.emaxhealth.com/1020/could-steroids-make-crohns-disease-worse For the first time The Scripps Research Instiitute (TSRI) scientists have identified a way some people with Crohn's disease may become resistant to steroids. According to their findings, steroids may even make things worse in some instances. The study The scientists focused on immune cells known as Th17 that are a type of white blood cell for their study. They found out that some Th17 cells express a protein called MDR1 and that these cells are linked to inflammation in Crohn's patients. MDR1 is also associated with drug resistance that develops with cancer. Biologist Mark Sundrud, a TSRI assistant professor who led the study said in a press release: "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." Just 5 to 10 percent of specialized immune cells produce MDR1-expressing TH17 cells in healthy individuals the study authors explain. The investigation found actively inflamed tissue taken from Crohn's disease patients contained almost 60 percent MDR1+ TH17 cells that are resistant to both natural and synthetic steroids. The overexpression of MDR1 is thought to be a protective mechanism. "If a T cell expresses MDR1, it is likely to have an unfair growth advantage over surrounding T cells," Sundrud explains. "When exposed to steroids, it's this subset of cells that will survive and thrive." The researchers are continuing to investigate whether the pro-inflammatory cells continue to accumulate over time, The finding helps explain how Crohn's disease develops, but more specifically why the disease can become resistant to steroid treatment that can ultimately lead to the need for surgery.