Clinical Impact of Immune Cells and Their Spatial Interactions in Diffuse Large B-Cell Lymphoma Microenvironment

Purpose: Tumor-infiltrating immune cells have prognostic sig-nificance and are attractive therapeutic targets. Yet, the clinical significance of their spatial organization and phenotype in diffuse large B-cell lymphoma (DLBCL) is unclear. Experimental Design: We characterized T cells, macrophages, and their spatial interactions by multiplex IHC (mIHC) in 178 patients with DLBCL and correlated the data with patient demo-graphics and survival. We validated the findings on gene expression data from two external DLBCL cohorts comprising 633 patients. Results: Macrophage and T-cell contents divided the samples into T cell-inflamed (60%) and noninflamed (40%) subgroups. The T cell-inflamed lymphoma microenvironment (LME) was also rich in other immune cells, defining immune hot phenotype, which did not as such correlate with outcome. However, when we divided the patients according to T-cell and macrophage contents, LME char-acterized by high T-cell/low macrophage content or a correspond-ing gene signature was associated with superior survival [5-year overall survival (OS): 92.3% vs. 74.4%, P = 0.036; 5-year progres-sion-free survival (PFS): 92.6% vs. 69.8%, P = 0.012]. High pro-portion of PD -L1-and TIM3-expressing CD163- macrophages in the T cell-inflamed LME defined a group of patients with poor outcome [OS: HR = 3.22, 95% confidence interval (CI), 1.63-6.37, P-adj = 0.011; PFS: HR = 2.76, 95% CI, 1.44-5.28, P-adj = 0.016]. Furthermore, PD-L1 and PD-1 were enriched on macrophages interacting with T cells. Conclusions: Our data demonstrate that the interplay between macrophages and T cells in the DLBCL LME is immune checkpoint dependent and clinically meaningful.