Lumaplate

MC57G target cells were pulsed with 2 μg mL⁻¹ of peptide, radiolabeled and incubated with effector splenocytes for 6 h at an effector‐to‐target cell ratio of 100:1. Maximum and spontaneous release controls were set up for each condition. Luma plate (PerkinElmer, MA, USA) were coated with 30 μL of the supernatant, allowed to dry overnight and counts recorded on a top count MicroBeta plate reader. Percent specific lysis was calculated using the following equation: [(sample ⁵¹Cr release − spontaneous ⁵¹Cr release)/(maximum ⁵¹Cr release − spontaneous ⁵¹Cr release)] × 100.

Frozen human peripheral blood mononuclear cells (PBMCs) were purchased from Precision Bioservices (Frederick, MD, USA). The PBMCs were thawed and washed with medium containing DNase (Roche Diagnostics, Mannheim, Germany). After overnight incubation, the PBMCs were used as effector cells. OC cells, as target cells, were labeled with approximately 3.7 MBq of Na₂⁵¹CrO₄ (PerkinElmer, Waltham, MA, USA) for 1 h at 37 °C. These target cells (1.0 × 10⁴ cells) were incubated with the anti-FOLR1 antibodies and PBMCs at an E:T ratio of 25:1 for 4 h at 37 °C. After incubation, each supernatant was transferred onto a LumaPlate (PerkinElmer) and dried sufficiently. The ⁵¹Cr radioactivity was measured using a microplate scintillation counter (TopCount NXT, PerkinElmer). After subtracting the radioactivity of the medium background from the radioactivity of each sample, the cytotoxicity was calculated using the following formula: % cytotoxicity = 100 × (S – Tspo) / (Total – Tspo), where S is the radioactivity of the experimental sample well, Tspo is the mean spontaneously released radioactivity of the target cells in the absence of antibody and effector cells (target cells incubated with medium alone), and Total is the mean radioactivity of the target cell lysis (target cells incubated with detergent).