IL21 and type 1 diabetes mellitus: This CD28 pro-inflammatory activity is particularly relevant in the context of inflammatory diseases, such as multiple sclerosis (MS) and type 1 diabetes (T1D), where CD28 individual stimulation may amplify the inflammatory response by up-regulating cytokines related to the Th17 cell profile phenotype, such as IL-6, IL-21, and IL-17A (37, 38).