The Immunology of DLBCL

SIMPLE SUMMARY: Diffuse large B-cell lymphoma (DLBCL) is the most common type of malignant lymphoid neoplasm and includes morphologically and molecularly heterogeneous disease subtypes. Genetic aberrations of tumor cells are strongly related to the signature of the tumor microenvironment. In this review, we summarize common genetic aberrations associated with immune escape, immune cell subs involved in DLBCL pathogenesis, and distinct microenvironmental signatures identified using next-generation sequencing and single-cell technologies. We also discuss the pathogenic role of immunosenescence in Epstein-Barr virus-positive DLBCL. Moreover, as DLBCL exhibits unique pathogenesis in immune-privileged sites, we also present a hypothetical model of DLBCL development in immune-privileged sites. ABSTRACT: Diffuse large B-cell lymphoma (DLBCL) is an aggressive malignancy and is the most common type of malignant lymphoid neoplasm. While some DLBCLs exhibit strong cell-autonomous survival and proliferation activity, others depend on interactions with non-malignant cells for their survival and proliferation. Recent next-generation sequencing studies have linked these interactions with the molecular classification of DLBCL. For example, germinal center B-cell-like DLBCL tends to show strong associations with follicular T cells and epigenetic regulation of immune recognition molecules, whereas activated B-cell-like DLBCL shows frequent genetic aberrations affecting the class I major histocompatibility complex. Single-cell technologies have also provided detailed information about cell–cell interactions and the cell composition of the microenvironment of DLBCL. Aging-related immunological deterioration, i.e., immunosenescence, also plays an important role in DLBCL pathogenesis, especially in Epstein-Barr virus-positive DLBCL. Moreover, DLBCL in “immune-privileged sites”—where multiple immune-modulating mechanisms exist—shows unique biological features, including frequent down-regulation of immune recognition molecules and an immune-tolerogenic tumor microenvironment. These advances in understanding the immunology of DLBCL may contribute to the development of novel therapies targeting immune systems.