Figure 4. Cytotoxicity of effector CTLs against HMEC. Target HMEC cells (3.7 × 10⁴ cells/well) were incubated in the presence of effector CTLs at a 1:8 ratio. After 3 d, floating CTLs were removed, target cells carefully washed with HBSS, attached HMEC were trypsinized and cell viability determined. Square size reflects viable target cell counts. Data was scaled to bring all controls (target cells incubated without CTLs) to equal values (25,000 cells). Data represent the mean value of 3 independent measurements. The standard deviations for the number of viable cells were in the 1,200–3,400 cell range. P values determined by t-test.