Disclosed are: a cell capable of expressing an exogenous GITRL or an exogenous GITRL derivative； a method for producing the cell； a therapeutic or prophylactic agent comprising the cell as an active ingredient； use of the cell in the manufacture of a therapeutic or prophylactic agent； a method comprising a step of administering the cell to a subject； a viral vector carrying a gene encoding a GITRL or a GITRL derivative； a therapeutic or prophylactic agent comprising the viral vector as an active ingredient； use of the viral vector in the manufacture of a therapeutic or prophylactic agent； and a method comprising a step of administering the viral vector to a subject.
