Abstract: A chimeric monoclonal antibody targeted at ricin, in which the light chain and heavy chain are such that: the constant region of the light chain and the constant region of the heavy chain are essentially made up respectively of the constant region of the light chain and the constant region of the heavy chain of human immunoglobulin, the variable region of the light chain and the variable region of the heavy chain include respectively the variable region of the light chain and the variable region of the heavy chain of macaque immunoglobulin, the monoclonal antibody not substantially inducing an immune response against chimeric antibodies.