CD274 and neoplasm: While PD-L1 expression by itself is not an indicator of TIL culture success, the ratio of CD8+ T cells to PD-L1+ cells is trending towards a significant separation, suggesting this important negative feedback loop may limit the ability to grow tumor-reactive TIL ex vivo. We subsequently performed unsupervised clustering of the data, which allowed us to further analyze the large amount of information generated with multispectral imaging.