The IL23R gene provides instructions for making a protein called the interleukin 23 (IL-23) receptor. This protein is embedded in the outer membrane of several types of immune system cells, including T cells, natural killer (NK) cells, monocytes, and dendritic cells. These cells identify foreign substances and defend the body against infection and disease.~At the cell surface, the IL-23 receptor interacts with a protein called IL-23. These two proteins fit together like a lock and key. IL-23 is a cytokine, which is a type of protein that regulates the activity of immune cells. When IL-23 binds to its receptor, it triggers a series of chemical signals inside the cell. These signals promote inflammation and help coordinate the immune system's response to foreign invaders such as bacteria and viruses.