Distinct threshold for the induction of survival and degranulation. (A) Dose-response curve based on the concentration of input anti-CD8. FcRγ-deficient BMMCs expressing CD8/γ were stimulated with various amounts of anti-CD8 mAb, and β-hex release (•) and cell viability (○) were measured at 30 minutes and 4 days, respectively. Responses were expressed as percentage of each maximum response. Data were means ± SDs of triplicate assays. Similar results were obtained from 4 independent experiments. (B) Dose-response curve based on the percentage of bound anti-CD8. The same cells were treated with the indicated amounts of anti-CD8, followed by staining with PE-labeled antirat Ig κ light chain (inset). Background-subtracted mean fluorescence intensity (MFI) for each concentration is shown. The responses shown in panel A are expressed based on the percentage of bound anti-CD8.