1. An antagonist of a delta-like ligand 4 (Dll4), used to prevent, treat or ameliorate type 1 or type 2 diabetes mellitus, where the antagonist blocks the interaction between Dll4 and Notch receptor, thereby increasing the number of T cells and preventing by curing or ameliorating diabetes. 2. A delta-like ligand 4 (Dll4) antagonist used to lower blood glucose in a subject in need thereof, where the antagonist blocks the interaction between the Dll4 and Notch receptor, and the blood glucose level decreases. 3. A delta-like ligand 4 (Dll4) antagonist used to reduce or block the production of autoantibodies in a subject in need of such a reduction or blocking, where the antagonist blocks the interaction between the Dll4 and Notch receptor, and the production of autoantibodies is reduced or blocked. 4. A method of preventing, treating, or ameliorating type 1 or type 2 diabetes mellitus, comprising administering to a subject in need of a therapeutically effective amount of a Dll4.5 antagonist. A method of lowering blood glucose, comprising administering to a subject in need of a therapeutically effective amount of a Dll4.6 antagonist. A method of reducing or blocking the production of autoantibodies, comprising administering to a subject in need of a therapeutically effective amount of a Dll4.7 antagonist. The Dll4 antagonist according to claim 3 or the method according to claim 6, wherein the autoantibodies are autoantibodies to insulin and autoantibodies to decarboxylase of glutamic acid 65 (GAD65) or to two of these proteins. The Dll4 antagonist according to any one of claims 1 to 3 and 7, or the method according to any one of claims. 4-7, in which the Dll4 antagonist is an antibody or its fragment, which are special1. Антагонист дельта-подобного лиганда 4 (Dll4), применяемый для предупреждения, лечения или ослабления сахарного диабета 1-го или 2-го типа, где антагонист блокирует взаимодействие между Dll4 и Notch-рецептором, тем самым повышая число Т-клеток и предупр
