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🌱 來自: What is PD-L1

Blockade of PD-1 or CTLA-4 Signaling in Tumor Immunotherapy

• T-cell receptor (TCR).
• This first signal is not enough to turn on a T-cell response, and a second signal delivered by the B7 costimulatory molecules B7-1 (or CD80) and B7-2 (or CD86) is required.
• Cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) is up-regulated shortly after T-cell activation and initiates negative regulation signaling on T cells during ligation with the B7 costimulatory molecules expressed by antigen-presenting cells.
• When these molecules bind to CD28, they provide activation signals; when they bind to CTLA-4, they provide inhibitory signals.
• The interaction between CTLA-4 and the costimulatory molecules happens primarily in the priming phase of a T-cell response within lymph nodes.
• Programmed death 1 (PD-1) inhibitory receptor is expressed by T cells during long-term antigen exposure and results in negative regulation on T cells during ligation with PD-L1 and PD-L2, which are primarily expressed within inflamed tissues and the tumor microenvironment.
• The PD-1 interaction happens in the effector phase of a T-cell response in peripheral tissues.
• Its blockade with antibodies to PD-1 or PD-L1 results in the preferential activation of T cells with specificity for the cancer.