CD274 and B-cell chronic lymphocytic leukemia: Peripheral CLL tumour cells in TCL1tg mice showed a modest increase in CD274 expression (MFIR 13·8 ± 8·0) as compared to WT B cells (MFIR 8·5 ± 7·5, P = 0·022), while lymph node-residing tumour cells exhibited a more pronounced increase (MFIR 14·0 ± 6·8 vs. 5·6 ± 3·3, P < 0·001), which suggests a microenvironment-induced upregulation of CD274 on tumour cells.