Sara Rahmati Miltenyi BiotecGermany

Spatial biology enables detailed analysis of molecular processes within native tissue architecture. Using MACSima® Imaging Cycling Staining (MICS), hundreds of proteins and dozens of RNA markers can be detected on the same section, generating high dimensional datasets that enhance cellular characterization and improve therapeutic target solutions. After an introduction into Miltenyi Biotec's innovative spatial biology and imaging solutions, we will demonstrate how B cells play a pivotal role in shaping the TME and tertiary lymphoid structures (TLS). The functions of specific B cell subsets in cancer pathogenesis remain unclear. Using a tissue-centric single-cell RNA-sequencing pipeline, flow cytometry, and high-plex spatial biology MACSima platform, we identify CD27⁻IgD⁻CD21⁺CD11c⁻ double negative 1 (DN1) B cells as a regulatory population enriched in RCC tumours and associated with worse prognosis. These cells localize within immature tertiary lymphoid structures near IL-10⁺ and TGFβ⁺ CD8⁺ T cells. TLR signalling drives their differentiation, and DN1 B cells suppress CD8⁺ T cell cytotoxicity partially via IL-10 and TGFβ. Our findings reveal a novel immune evasion mechanism with potential diagnostic and therapeutic relevance.