CD4 and systemic sclerosis: ATO 2.5 μg/g + CuCl2 significantly decreased CD25 levels on CD4+ T lymphocytes by 23% (p<0.01) compared to the HOCl-SSc-mice and reached the level observed in the PBS-control group and in the HOCl-SSc group treated with high dose ATO 5 μg/g (p<0.05) (Figure 4D).