(b) Luciferase activity in Jurkat cells transfected with the fusion in a (Slamf1-CD3ζ) or a fusion of SLAM ectodomain construct lacking the immunoglobulin V domain and CD3ζ (ΔIgV-Slamf1-CD3ζ), and luciferase reporters as in a, then exposed to heat-killed E. coli F18. 