Primary central nervous system diffuse large B-cell lymphoma has poorer immune cell infiltration and prognosis than its peripheral counterpart

Aims: Primary central nervous system (CNS) diffuse large B-cell lymphoma (PCNSL) is an ominous disease with a poor prognosis. The brain is an immune-privileged sanctuary, and this may contribute to an ineffective host immune response and thus a poorer outcome. The aim of this study was therefore to study the difference in the immune composition in PCNSL and non-CNS diffuse large B-cell lymphoma (DLBCL), and the role of the immune response in PCNSL prognosis. Methods and results: Thirty-two biopsy specimens of PCNSL and 30 specimens of low-stage non-CNS DLBCL from immunocompetent patients formed the study group. The density and distribution of immune cells, including dendritic cells (dendritic cell-specific lysosomal-associated membrane protein-positive and S100-positive), effector/memory T cells (CD45RO-positive), and cytotoxic T cells (granzyme B-positive), and the expression of HLA-DR by lymphoma cells, were evaluated immunohistochemically. PCNSL patients showed poorer overall survival (P = 0.032). On comparison of the PCNSL and DLBCL biopsy specimens, the PCNSL cells showed less HLA-DR expression (P = 0.003), and there were fewer S100-positive cells (P < 0.01), and effector T cells (P = 0.026) infiltrating PCNSL than infiltrating DLBCL. For PCNSL patients, fewer cytotoxic T cells in the background constituted a poor prognostic factor (P = 0.004). Intratumoral S100-positive cell infiltration was positively correlated with T-cell infiltration, and a T-cell rimming pattern. Conclusions: In PCNSL, the baseline antitumour immune response is less as compared with non-CNS DLBCL, and this response may play a role in the poorer prognosis. Adjuvant dendritic cell and T-cell immunotherapy may further boost treatment responses in PCNSL patients.