Brief description of mechanism described in immune checkpoint 3D animation video
High complexity and specificity of the immune system require many rules and checkpoints to prevent autoimmunity and to “brake” immune response. One of them is shown in our immune checkpoint 3D animation video. Tumor cells show more changes in genetics and epigenetics than normal cells, which can theoretically produce sufficient amounts of antigens so that the immune system can distinguish them and trigger immune responses. However, immunosuppression makes it difficult to produce an effective immune response against tumor cells. These suppression signals are so-called immune checkpoints.
On the one hand, these suppression signals are involved in maintaining the immune tolerance of autoantigen, avoiding autoimmune diseases and injuries caused by excessive activation of an immune response. On the other hand, tumor cells can hide from immune recognition by suppressing the activation of T cell through immune checkpoints. Up till now, several molecular mechanisms of tumor cells’ escape from the immune recognition have been defined, such as tumor infiltrating macrophages which may limit activation and proliferation of T cell by interfering with amino-acid metabolism. Therefore, activating T cells through different strategies is the crucial focus of tumor immunotherapy, among which blockade of immune checkpoints is one of the most effective strategies.
What is PD-1 and why it is mentioned in immune checkpoint 3D animation video
PD-1 (programmed cell death protein-1) is a kind of important immunosuppressive transmembrane protein expressing on the surface of the T cells. PD-1 mainly restricts the activities of T cells in chronic inflammation, infection or cancer. It has two ligands, PD-L1 and PD-L2, which are related proteins found in antigen presenting cells and cancer cells. Tumor cells express PD-L1 or PD-L2, which can help tumor cells escape from the immune system by attaching to PD-1 protein on the surface of T cells. When ligands bind to PD-1, T cells cannot detect tumor cells, and the signal of attacking tumor cells will be blocked. Meanwhile, PD-1 reduces the threshold of apoptosis and induces energy of the immune system through the passivated T cell receptor signal, which usually leads to the depletion of the T cell.
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