Fig 1: 4MU blocks activation and polarization of naive CD4 T cells into Th1 cells.CFSE-stained naive CD4+ T cells from C57BL/6 mice (n = 3) were stimulated for 5 days with anti-CD3E, anti-CD28, or rhIL-2 ± 4MU (100 μg/mL) and then flow analyzed to quantify expression of CD25 (A and E), CD69 (B and F), CD279 (C and G), and CFSE dilution (D and H). CFSE-stained naive CD4+ T cells from C57BL/6 mice (n = 3) were stimulated and polarized toward Th1 cells for 5 days with anti-CD3E, anti-CD28, rhIL-2, rmIL-12, or anti–IL-4 ± 100 μg/mL 4MU and then flow analyzed for expression and quantification of IFNG (I and K) and CFSE dilution (J and L) (flow gating strategy shown in Supplemental Figures 6 and 7). Data are represented as mean ± SEM and analyzed using 1-way ANOVA followed by Tukey’s post hoc test for multiple comparisons. *P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001.