An object of the present invention is to provide a drug and a method for effectively inducing donor specific immune tolerance in a recipient in transplantation therapy. A complex of an siRNA for a costimulatory factor and schizophyllan is delivered to a Dectin-1 expressing cell which specifically recognizes schizophyllan to regulate the function of the Dectin-1 expressing cell, and therefore can induce immunosuppression effect as well as induce immune tolerance effectively.