Immunotoxins composed of monoclonal antibodies (mAbs) and various toxins have been developed for the treatment of malignancies. We investigated the efficacy of three ricin toxin A-chain (RTA)-containing immunotoxins (ITs) conjugated from mAbs which recognize glycolipid asialo-GM2 and glycoprotein H-2d. These ITs retained the same immunoreactivity with mAbs. We evaluated the cytotoxicity of these ITs against mouse lymphoma cells L5178Y variants showing high (AA12,CC9) and low (27AV) expression of asialo-GM2. Anti-H-2d-RTA IT had the strongest cytotoxicity for all cell lines. Anti-asialo-GM2 (IgM)-RTA IT had stronger cytotoxicity than anti-asialo-GM2 (IgG3)-RTA IT. Anti-asialo-GM2-RTA ITs had different cytotoxicity against AA12 and CC9 cells. The establishment of appropriate anti-glycolipid mAbs may lead to effective immunotargeting therapy.</p
