RESUMO
The data presented demonstrate that a human-murine chimeric antibody has been generated that retains the immunoreactivity and has similar pharmacokinetic properties of its parent murine monoclonal antibody NRML-05. A competitive ELISA assay demonstrated that antigen reactivity of both parent and chimera were nearly identical. In a direct cell binding assay, NRML-05 and chimeric antibodies were immunoreactive, 81% and 83%, respectively. Scatchard Analysis of the antibodies indicate very similar affinities for NRML-05 (4.4 x 10(9) M-1) and chimera (2.7 x 10(9) M-1). Localization of the two antibodies to tumor xenografts in nude mice were very similar in biodistribution studies. The chimeric antibody is not as well recognized by antiglobulin from patients who have responded to non-idiotypic murine antibody determinants. Although this data does not predict how immunogenic a chimera would be in the clinical setting, it does suggest that patients without significant anti-idiotypic antiglobulin response could benefit from second and subsequent administrations with chimeric antibody. Even though anti-idiotypic responses may occur with the chimera, these may be reduced as a result of the presentation of these epitopes on the less immunogenic human constant domains.
Assuntos
Anticorpos Monoclonais/imunologia , Anticorpos Antineoplásicos/imunologia , Melanoma/imunologia , Proteínas de Neoplasias/imunologia , Animais , Anticorpos Monoclonais/genética , Anticorpos Antineoplásicos/genética , Especificidade de Anticorpos , Antígenos de Neoplasias , Epitopos/imunologia , Genes Sintéticos , Humanos , Imunoglobulina G/genética , Melanoma Experimental/diagnóstico por imagem , Antígenos Específicos de Melanoma , Camundongos , Camundongos Nus , Cintilografia , Proteínas Recombinantes/genética , Proteínas Recombinantes/imunologiaRESUMO
IgE has clinical importance because it is responsible for immediate hypersensitivity. Studies of IgE expression in rats appear to contradict current models for immunoglobulin gene expression. To study rat IgE expression at the RNA and DNA levels, we have constructed a cDNA for part of the rat epsilon (epsilon) heavy chain that is expressed by a rat myeloma, IR162. The rat epsilon-chain clone was initially identified by an efficient selection scheme. DNA sequencing of the 580-bp cDNA revealed that it encoded 176 amino acids that were 50% homologous to the human epsilon H chain. The sequence begins near the end of the CH2 domain and ends 31 amino acids into the CH4 domain. Cysteines important for the structure of the human IgE were conserved in the rat epsilon H-chain. The identity of the cloned epsilon cDNA was confirmed by comparison with a portion of the constant region gene for mouse epsilon H chain. The mouse and rat nucleotide sequences were 79% homologous.
