Abstract: A process for producing chimeric antibodies using novel recombinant DNA vectors and homologous recombination in vivo is described. The recombinant DNA constructs of the invention can be used to transfect antibody producing cells so that targeted homologous recombination occurs in the transfected cells leading to gene modification and the production of chimeric antibody molecules by the transfected cells.

Abstract: Novel polypeptides, polynucleotide sequences, DNA constructs and compositions are provided for the preparation and use of polypeptides associated with naturally occurring polypeptides found in brains. The small molecular weight polypeptides are growth inhibitors for neoplastic cells without inhibiting normal cells. The polypeptides comprise specific regions which are highly conserved, separated by less conserved regions. The polypeptides find use in inhibiting neoplastic growth and detecting receptors for the polypeptides. Antibodies are provided in conjunction with the polypeptides, which may be used together or separately for detecting the presence of the neoplastic cell retarding polypeptides.