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. Author manuscript; available in PMC: 2018 Jun 20.
Published in final edited form as: Semin Oncol. 2007 Apr;34(2):165–172. doi: 10.1053/j.seminoncol.2006.12.004

Figure 1.

Figure 1

Antigen is presented in the context of major histocompatibility (MHC) molecules to T-cell receptor (TCR), referred to as signal 1, and costimulatory molecules, such as CD28 and B7, provide signal 2 to allow for T-cell activation. T-cell responses are then regulated by CTLA4 interaction with B7 so as to maintain homeostasis. Regulatory T cells can also suppress T-cell activation. In cancer patients, it is possible to interfere with the CTLA4-B7 interactions with anti-CTLA4 antibody thereby promoting enhanced T-cell responses.