To obtain a new hybridoma free from immuno-cross-reactivity having high titer useful for diagnosis or the like of nervous tissue by producing a monoclonal antibody capable of recognizing all the isoforms of a specific clathrin assembly-protein 3 as the antigen.

The hybridoma produces the monoclonal antibody capable of recognizing all isoforms of the clathrin assembly-protein 3 including the amino acid sequence of formula I as the antigen, the hybridoma having the depositing number of FERMBP-6379, and the produced monoclonal antibody manifests titer of 2 to 4 times of that of the monoclonal antibody having the same antigen-recognition specificity, produced by the hybridoma R-18 cultured in the spume condition. This monoclonal antibody is capable of recognizing the 388 to 394 position of the amino acid sequence of the clathrin assembly- protein 3 described in formula II, and preferably labeled by protein, fluorescent dye or radio isotope.