The present invention relates to a monoclonal antibody or fragment thereof, which binds specifically to the cyclin-dependent kinase 5 (Cdk5) activating protein, p25 and not to p35, a hybridoma cell line producing the monoclonal antibody, and methods for the detection and/or isolation of p25, p25 fragments or homologs thereof from biological material. The invention further relates to the use of the monoclonal antibody or fragment thereof for detection and treatment of neuronal disorders and cancers.
