Ablation of Crbn augments T-cell activation and function. CRBN protein (A) and mRNA (B) levels following anti-CD3ε/anti-CD28 stimulation of mouse (C57Bl/6) T cells. (C) Number of transcriptional changes after anti-CD3ε+anti-CD28 stimulation of Crbn^+/+ T cells, Crbn^−/− T cells, or both (Shared). (D) Crbn^+/+ and Crbn^−/− CD4⁺ and CD8⁺ T-cell proliferation after 72 hours of 5 μg/mL anti-CD3ε^+/−/1 μg/mL anti-CD28 stimulation, as measured by CellTrace Violet (CTV), quantified by the division index (mean number of divisions per cell). (E) Production of IL-2 and IFN-γ after 72 hours of activation in Crbn^+/+ and Crbn^−/− T cells after stimulation with anti-CD3ε^+/−/anti-CD28. (F) Fold change in levels of the indicated mRNAs (determined by qRT-PCR) after activation of Crbn^+/+ and Crbn^−/− CD8⁺ T cells for 12, 24, 48, and 72 hours, relative to levels of B2M (β₂-microglobulin) mRNA: Ifng (i), Tbx21 (ii), Eomes (iii), and Gzmb (iv). (G) Images of representative B16 melanoma tumors in Crbn^+/+ and Crbn^−/− recipient mice and (H) tumor growth over time in these 2 cohorts. (I-J) CD44 cell surface expression and Trp2-peptide reactivity of CD8 tumor-infiltrating lymphocytes from B16 tumor-bearing Crbn^+/+ and Crbn^−/− mice (day 10). (K) Tumor growth of B16 tumor-bearing mice after adoptive cell transfer of Crbn^+/+ and Crbn^−/− T cells and treatment with IL-2 twice a day (arrows). All results are representative of at least 2 independent experiments in at least 3 mice (excluding microarray analysis). n.s., not significant; *P < .05; **P < .01; ***P < .001; ****P < .0001.