In vitro Cytolysis of B-Lymphoma Cells Mediated by an Anti-CD3/Anti-CD20 Bispecific Single-chain Antibody

Recently we have generated a novel anti-CD3/anti-CD20 bispecific single-chain antibody (bscCD3×CD20) capable of cross-linking CD20 positive tumor cells and CD3 positive T cells. Here we have analyzed the in vitro efficacy of bscCD3×CD20 in mediating Ramous human B-lymphoma cell lysis in the presence of T-enriched human peripheral blood lymphocytes (PBLs). Obvious apoptosis characters were observed by Annexin V/PI (AV/PI) stained and scanning electron microscopy. As evaluated by a nonradioactive cytotoxicity assay, bscCD3×CD20 showed potent bioactivity of mediating human B-lymphoma cell lysis in the presence of T-enriched human PBLs. The potency of cytotoxicity depended on the ratios of effect cells to target cells (E:T) used. Further, the antibody showed a dose- and time-dependent effect on the mediating Ramous cells lysis. The specific lysis reached about 87.3% at an antibody concentration of 5 μg/mL with the ratio of the E:T used being 10:1. Clear changes in apoptogenes expression profiles were detected by apoptosis gene array after Ramous cells were treated with the antibody and PBLs. Among the upregulated apoptogenes, ATM and p53 showed an increase of 187 times and 15 times, respectively, which suggested that the ATM-p53 pathway may be the main apoptosis way of Ramous cells being induced by T cells in the presence of the bscCD3×CD20.