CD274 and cancer: B cells can act as antigen presenting cells and have low basal IC expression that can be upregulated upon activation.41 While tumor-infiltrating B cells have been studied, their function within the tumor microenvironment (TME) is unclear with some studies suggesting tumor-promoting effects, while others show that they can improve cancer outcomes.42–45 Splenic B cells had higher PD-L1 and PD-1 expression prevalence in aged versus young (Figure 2B).