CTL assay. The Lyt2⁺-AR1 mouse CTL line was cocultured with irradiated BALB/c spleen cells for 6 days. AR1 cells were washed and plated at increasing E:T ratios (0.5:1, 1:1, 2.5:1, 5:1, 10:1, 20:1) with ⁵¹Cr-labledBALB/c as targets in the presence or absence of CD31 peptide (200 μg/mL). Results are expressed as mean percent specific ⁵¹Cr release from triplicate wells and are reprecentative of 3 separate experiments.