PROBLEM TO BE SOLVED: To provide an agent for enhancing immunotolerance effect of donor specific transfusion (DST).SOLUTION: This invention relates to an agent for enhancing the effect of donor specific transfusion, comprising a [1,2,4] triazolo [1,5-a]pyrimidine derivative or its pharmaceutically acceptable salt.COPYRIGHT: (C)2015,JPO&INPIT【課題】ドナー特異的輸血(DST)による免疫寛容効果を増強するための薬剤を提供すること。【解決手段】[1,2,4]トリアゾロ[1,5-a]ピリミジン誘導体又はその医薬上許容される塩を含む、ドナー特異的輸血の効果増強薬。【選択図】なし