CD4 and melanoma: In CM patients, Treg levels were shown to correlate with clinical activity, thus demonstrating the utility of immune cell detection in the monitoring of melanoma progression, while MDSCs promote the differentiation of CD4+ T-cells into CD4+/CD25+/Foxp3+ cells, which express TGF-β and IL-10 as well as CTLA-4 and PD-1.