The immune checkpoint is a series of molecules expressed on immune cells that can regulate the degree of immune activation, playing a crucial role in preventing autoimmune reactions. When the body's immune function is stimulated, it is activated but not excessively so, as the "immune checkpoint molecules" act like a braking system in a car, able to timely apply the brakes during immune system activation to maintain it within a normal range, preventing overactivation. Abnormal expression and function of immune checkpoint molecules are significant factors in many diseases. For example, if these molecules are overexpressed or their function is too strong, immune function is suppressed, leading to reduced immune response. Conversely, if the immune inhibitory function of immune checkpoint molecules is poor, immune function becomes abnormal. Tumor cells can express certain substances that activate immune checkpoints, essentially applying the brakes, preventing antigens from being presented to T cells, disrupting the process in the tumor immune environment and inhibiting T cell immune function, allowing the tumor cells to escape surveillance and survive.
