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Fig. 1 | Cell & Bioscience

Fig. 1

From: Anti-CTLA-4 antibodies in cancer immunotherapy: selective depletion of intratumoral regulatory T cells or checkpoint blockade?

Fig. 1

The prevailing view: CTLA-4 checkpoint blockade results in tumor immunity. Activation of T cells requires two signals. One is the binding of the T cell receptor (TCR) to the MHC-antigen peptide complex presented by antigen presenting cells (APCs) (signal 1). The other one is the binding of B7 molecules (B7-1 or B7-2) to the co-stimulatory (+) molecule CD28 on the surface of T cells (signal 2). With higher affinity than CD28, inhibitory (−) CTLA-4 binds to B7 ligands on APCs and provides a brake  for T cell activation. Anti-CTLA-4 antibodies were proposed to release brakes of naïve T cells and allow them to be activated in the lymphoid organs and then migrate to tumors to cause tumor rejection

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