Abstract: The invention relates to a modified antibody which contains two or more H chain V regions and two or more L chain V regions of monoclonal antibody and can transduce a signal into cells by crosslinking a cell surface molecule(s) to thereby serve as an agonist. The modified antibody can be used as a signal transduction agonist and, therefore, useful as a preventive and/or remedy for various diseases such as cancer, inflammation, hormone disorders and blood diseases.