Figure 4. mCII_707–721–specific NKT cell activation engages TCR and requires costimulation.

(A) Activation of mCII_707–721–specific NKT cells operated through TCR signaling. Percentage of phosphorylated ZAP70-positive cells in NK1.1⁺ T cells by FACS shows a significant increase over nonstimulated cells upon mCII_707–721 stimulation in vitro, with abrogation by blocking anti-CD1 (1B1, 10 μg/ml). (B) Costimulatory signals for proliferation after in vitro stimulation of LNCs from mCII_707–721–immunized mice. Blocking with antibodies to costimulatory proteins significantly reduced proliferation. Data are mean ± SD, n = 4. **P ≤ 0.01; ***P ≤ 0.001.