The multifaceted roles of tumor-infiltrating plasma cells in cancer immunology.

Activated B cells differentiate into plasma cells that can produce a vast repertoire of antibodies. The discovery of tumor-infiltrating plasma cells (TIPCs) has highlighted the importance of their interactions with the host immune system in cancer hallmarks. Notably, tertiary lymphoid structures (TLSs) serve as crucial sites for TIPC generation, supporting activation, maturation, and class-switch recombination (CSR). These structures strongly influence the functional orientation of TIPCs and are often associated with favorable clinical outcomes in various cancers. CSR further diversifies antibody isotypes, enabling distinct effector functions. Nevertheless, there are still large controversies over the exact roles of TIPCs, with evidence pointing to both pro- and antitumor activities depending on the tumor context. In this review, we revisit the basics of plasma cell biology, the impact of TLSs and CSR on TIPC function, and the contrasting effects of TIPCs on tumor progression and immune responses. We aim to provide further insights into the potential utility of targeting plasma cell biology as therapeutic approaches for cancer patients in clinical settings.