Effects of 4-1BB agonistic antibody on the T cell functional phenotype. Peripheral blood mononuclear cells were stained with antibodies to CD3, CD4, CD8, CD44 and CD62L on day 14 or day 22 post-tumor implant. CD3 + CD8+ and CD3 + CD4+ T cells were further evaluated for T central memory (Tcm) (CD44 + CD62L+), T effector memory (Tem) (CD44 + CD62L-), and T naïve (CD44loCD62Lhi) cell subsets. The ratio of CD8 to CD4 T cells is shown (a). The percentage of CD4 and CD8 T cell populations in treated versus untreated mice is also shown (a, b, c) as well as the percentages of the different CD4 and CD8 cell subsets: Tcm (e, h), Tem (f, i) and T naïve cells (d, g), represented as a percentage of the parental population gate. *p < 0.05, **p < 0.01, ***p < 0.005 by t-test, n ≥ 3 mice/group, data is representative of 3 independent experiments.