PROBLEM TO BE SOLVED: To provide a new and useful means for using siRNA, antigen-presenting cells, and regulatory T cells.SOLUTION: A modified APC, i.e., an antigen-presenting cell (siRNA-modified, antigen-sensitized APC) modified with siRNA and sensitized with an antigen, is disclosed. An antigen-specific regulatory T cell (antigen-specific Treg) which is antigen-specific and which is derived from a naive T cell using the siRNA-modified, antigen-sensitized APC is disclosed. A therapeutic drug having the antigen-specific Treg (regulatory T cell) as an effective component is disclosed, and others.【課題】siRNA、抗原提示細胞及び制御性Ｔ細胞の新規で有用な利用手段を提供する。【解決手段】siRNAで修飾されると共に抗原を感作された抗原提示細胞（siRNA修飾・抗原感作APC）である修飾APC。siRNA修飾・抗原感作APCを用いてナイーブＴ細胞から誘導される抗原特異的な制御性Ｔ細胞（抗原特異的Treg）。抗原特異的Tregを有効成分とする治療薬。その他。【選択図】図１０
