Definition of the CTL epitope. Mice were immunized two times with 40 μg of MAP4(PyCSP57–70) plus 15 μg of Lipofectin. Results shown are those of the CTL assay done with splenocytes removed 14 days after the second immunization. Target P815 cells were coated with 1 μM PyCSP59–70, PyCSP57–70, PyCSP57–66, PyCSP58–67, PyCSP59–68, PyCSP60–69, or PyCSP61–70 or the irrelevant peptides, PfSSP2-15 and PfSSP2-9. E:T Ratio, effector/target cell ratio.