CD4 and neoplasm: The observation that the percentage of NM-neoAg-specific CD4+ and CD8+ Teff cells expressing PD-1 increased upon chemotherapy indicates that NM-neoAgs, generated by chemotherapy-dependent apoptosis, principally activate and expand PD-1+ tumor-specific CD4+ and CD8+ T cells, providing thus the substrate on which anti-PD-1 therapy can perform its boosting effect directed towards the PD-1+ tumor-specific cell population14,17.