Increased anti-CD3–induced proliferation of SOCS3-deficient CD8+ T cells. (A) CFSE-labeled T cells were purified from wt (+/+) or Socs3ΔLck/ΔLck (Δ/Δ) LN cells and stimulated with 1.25 μg/mL anti-CD3 for 3 days. (B) Purified CD8+ T cells were labeled with CFSE and stimulated with 5 μg/mL anti-CD3+ at the indicated concentrations of anti-CD28 for 3 days. The division index shows the average number of cell divisions in each culture. Data are representative of 2 to 3 independent experiments.