However, CD28 may also function as a pro-inflammatory or anti-inflammatory role depending on the type of cell and the context in which it is expressed.[42] CD28 is required for both thymic development and peripheral homeostasis of Treg cells.[43] It has been demonstrated that CD28 prevents spontaneous autoimmunity by promoting the anti-inflammatory function of the Treg cells.[44] CD28 plays such an important role in the anti-inflammatory effects of Treg cells that it is reasonable to assume that CD28 expression on Treg cells is inversely associated with the risk of Crohn disease. This evidence concerns the gene CD28 and Crohn disease.