Considering the susceptibility of AIRmax mice to B16F10 development and the increased presence of CD4+/CD25+ cells in the early tumor growth stages, we speculated that CD4+/CD25+ cells represent the regulatory T cell population, which could suppress the antitumor response, allowing a higher incidence of tumors in AIRmax than in AIRmin mice [34, 35]. This evidence concerns the gene CD4 and neoplasm.