CD4 and neoplasm: Kates et al. [92] reported that a considerable group of BCG non-responders show pre-treatment co-localisation of PD-L1 in areas with a high density of CD8+ cells and a low density of CD4+ T cells, whereas BCG-responsive tumours are rich in CD8+ and CD4+ T cells and show almost no PD-L1 expression [92].