Immune checkpoints are a series of molecules expressed on immune cells that regulate the degree of immune activation. They play a crucial role in preventing autoimmune reactions where the immune system attacks normal cells. When the body's immune function is stimulated, it becomes activated but not excessively so, thanks to the "immune checkpoint molecules" acting like a brake system in a car. This timely braking helps maintain the immune system's activation within normal limits, preventing overactivation. Abnormal expression and function of immune checkpoint molecules are significant factors in the development of many diseases. If these molecules are overexpressed or too strong, immune function is suppressed, leading to reduced immunity. Conversely, if the immune inhibitory function of these molecules is poor, immune function becomes abnormal. Tumor cells express substances that activate immune checkpoints, which act as a brake to prevent antigen presentation to T cells. This hinders the antigen presentation process in the tumor immune microenvironment, inhibiting the immune function of T cells and allowing the tumor to evade surveillance and survive.
