B72.3 is a mouse monoclonal antibody against a tumour-associated antigen, TAG72, which recognizes breast, ovarian and colorectal tumour tissue. A mouse-human chimeric version of B72.3 has been expressed in Chinese-hamster ovary cells. This molecule has the binding specificity of B72.3 and constant regions from human IgG4. The chimeric B72.3 assembles to intact IgG and recognizes TAG72 as well as B72.3 in competitive binding assays. A proportion of the chimeric B72.3 (approx. 10%) does not form inter-heavy-chain disulphide bonds but still assembles into the IgG tetramer. This appears to be a general property of human IgG4 molecules. Co-expression of the chimeric light chain with a chimeric Fd' gene resulted in the expression of functional Fab'. Very little F(ab')2 is produced, although the Fab' can be oxidized to the dimeric F(ab')2 in vitro. The production of Fab' and F(ab')2 by this method is an attractive alternative to proteolytic digestion of IgG. The ability to produce these molecules in large quantities will allow the production and testing of a range of anti-tumour antibody and antibody fragment conjugates.
Abstract-We study the ionic conductivity versus temperature and frequency of large Na*S single crystals by using a calibrated impedance apparatus. The experimental setup used for the ionic conductivity measurements up to 1350 K and its calibration are described. The apparatus allows to measure complex impedances between 0.1 0 and 10 GfI. The high temperature conductivity data were. analyzed in terms of the conventional Frenkel defect model. We assume that cation vacancies and cation interstitials are the dominant intrinsic defects. The energy of motion was found to be 0.61 2 0.05 eV for a cation vacancy. The energy of formation of a Frenkel defect pair is 2.5 1 2 0.05 eV. Results are given that show clear evidence of a superionic behaviour close to the melting point, similar to the one found in alkaline earth fluorides and several halides. Furthermore, X-ray diffraction experiments on a high optical quality single crysq were performed. The cell parameter and the population parameter of Na+ were accurately determined (6.5373 A and 0.988, respectively). 0 1997 Elsevier Science Ltd.
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