Immunoglobulin G1, anti-(human CD20 (antigen)) (mouse monoclonal IDEC-Y2B8 γ1-chain), disulfide with mouse monoclonal IDEC-Y2B8 κ-chain, dimer, N-[2-[bis(carboxymethyl)amino]-3-(4-isothiocyanatophenyl)propyl]-N-[2-[bis(carboxymethyl)amino]-2-(methyl)-ethyl]glycine conjugate