Therefore, the aim of this study is to evaluate a correlation between presence of CD4+, CD8+, CD20+, CD25+ and FoxP3+ tumor-infiltrating lymphocytes (TILs), and clinico-pathological features of bladder cancer, as well as to assess blood Treg (i.e., CD4+CD25+FoxP3+) frequency before (Treg-pre) and after (Treg-post) tumor excision in the early (pT1–pT2) and late (pT3–pT4) phases of tumor development. Here, CD4 is linked to urinary bladder carcinoma.