CD4 and mixed connective tissue disease: In the forerunner medical condition for systemic autoimmune diseases, denoted as undifferentiated connective tissue disease (MCTD), the assessment of Treg cells showed that the percentage and absolute number of natural Tregs (CD4+CD25brightFoxP3+) were diminished in UCTD patients compared with healthy subjects, while the number of inducible Tregs (CD4+IL-10+) was increased [23].