CD4 and neoplasm: After tumor cell implantation, unlike in WT mice, the spleen of IL-30KO mice lacked the expansion of the CD4+CD25hiFoxp3+ regulatory T (Treg) cell population (IL-30KO mice: 5.64 ± 2.23% versus WT mice: 19.33 ± 5.60% of the total number of CD4+ cells.