CD69 and systemic sclerosis: Intriguingly, and in line with that observed in other autoimmune diseases, the expression of CD69 on CD4+ effector T cells was significantly increased in all SSc patients compared to controls and followed an inverse correlation with the CD69 expression on CD25high or FoxP3high cells suggesting, that the regulation of CD69 expression is specifically altered on the Treg population in SSc [47], [48], [49] (Figure 2d).