The results presented in this study have clinically relevant implications: (i) CD4+ TILs with TCRs directed against neoepitopes may kill autologous tumour cells and (ii) repeated exposure of TILs to the tumour cells (expressing neoantigens) can refine the TCR repertoire to produce a more focused immune response; (iii) PBMCs may be used as a viable source for T cells directed against tumour mutations and (iv) microdissection of tumour tissue may help achieve a more precise extraction and biologically relevant expansion of TILs. The gene discussed is CD4; the disease is neoplasm.