Kind Code: A1 Rejection in various organ transplants, allergic diseases, autoimmunity based on PI3Kδ selective inhibitory action and / or IL-2 production inhibitory action, and / or B cell proliferation inhibitory action (including activation inhibitory action) A novel and excellent method for preventing or treating diseases and blood tumors is provided. A trisubstituted triazine or a trisubstituted pyrimidine derivative exhibits a PI3Kδ selective inhibitory action and / or an IL-2 production inhibitory action and / or a B cell proliferation inhibitory action (including an activation inhibitory action)； and Rejection in various organ transplants, allergic diseases (asthma, atopic dermatitis, etc.), autoimmune diseases (rheumatoid arthritis, psoriasis, ulcerative colitis, Crohn's disease, systemic lupus erythematosus, etc.), or blood tumors (leukemia, etc.) Thus, the present invention has been completed. [Selection figure] None【課題】ＰＩ３Ｋδ選択的阻害作用及び／又はＩＬ－２産生抑制作用、及び／又はB細胞増殖抑制作用（活性化抑制作用を含む）に基づく、種々の臓器移植における拒絶反応、アレルギー疾患、自己免疫疾患、及び血液腫瘍等の新規かつ優れた予防又は治療方法を提供する。【解決手段】三置換トリアジン又は三置換ピリミジン誘導体がＰＩ３Ｋδ選択的阻害作用、及び／又はＩＬ－２産生抑制作用、及び／又はB細胞増殖抑制作用（活性化抑制作用を含む）を示すこと、そして種々の臓器移植における拒絶反応、アレルギー疾患（喘息、アトピー性皮膚炎等）、自己免疫疾患（関節リウマチ、乾癬、潰瘍性大腸炎、クローン病、全身性エリテマトーデス等）、又は血液腫瘍（白血病等）等の予防又は治療剤となりうることを知見して本発明を完成した。【選択図】なし
