Positive: both Docetaxel and untreated patients exhibited high frequencies of myeloid-derived suppressor cells (MDSC) (HLA-DRlow/negLin−CD11b+CD33+) as compared to healthy donors. MDSC iNOS expression and frequency of circulating Treg (CD3+CD4+CD25hiCD127low) were significantly higher in both groups of prostate cancer patients than healthy controls. MDSC levels were significantly higher in patients with three negative prognostic factors (elevated LDH, AP, PSA, anemia) vs. ≤1. Here, CD4 is linked to prostate cancer.