<p>It is intended to provide a rodent immune response regulatory protein having an amino acid sequence represented by SEQ ID NO:2 or 4; an immune response regulatory gene encoding this protein; and a method of constructing an arbitrary antibody in a rodent with the use of the same. By immunizing an experimental animal with the above-described protein and a fused protein thereof, immunization can be effectively performed and various polyclonal and monoclonal antibodies can be conveniently obtained. Since immunization can be efficiently carried out in experimental animals, model mice of immunopathy such as auto immune diseases can be efficiently constructed.</p>
