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![A primer on recent developments in cancer immunotherapy, with a focus on neoantigen vaccines](https://image.oaes.cc/f90be132-bf27-4e79-b7e1-c5bb6f88750b/2355.fig.2.png)
Figure 2. Differences in recognition and downstream processes between CD8+ and CD4+ T cells. CD8+ T cells recognize pMHC-I complexes, where the peptide is a fragment from an endogenous protein typically 8 to 11 AAs in length, which occupies a groove that is closed on both ends. CD4+ T cells recognize pMHC-II complexes, where the peptide is derived from cells or antigens engulfed by the APC and is typically longer, 12 to 25 AAs in length. The MHC-II groove is open on both ends. After activation, CD8+ T cells differentiate into cytotoxic T lymphocytes (CTLs), whereas CD4+ T cells differentiate e.g. into T helper cells, depending on receipt of further cytokine signals. APC: antigen-presenting cell; MHC: major histocompatibility complex; TCR: T cell receptor