Targeting of the CD161 Inhibitory Receptor Enhances Bone Marrow-Resident Memory CD8+ T Cell-mediated Immunity Against Multiple Myeloma [CART scRNA-seq]

Immune checkpoint inhibitors (ICIs) have transformed the treatment of many solid tumors. Still, their effectiveness in multiple myeloma (MM) remains underwhelming, highlighting the need to explore alternative approaches beyond conventional ICIs. Here, we identify CD161 as a novel inhibitory receptor on bone marrow resident memory CD8+ T cells (BM CD8+ TRMs), known for their sustained presence and vital role in local immune surveillance in MM BM tumor microenvironment. The CD161-CLEC2D axis, where CD161 interacts with CLEC2D on MM cells, mediates immune suppression and TRMs dysfunction. Blocking CD161 enhances TRMs function, including tissue residency, proliferation, and antitumor activity. Combining CD161 blockade with CAR-T therapy significantly alleviates CAR-T exhaustion, improving its therapeutic efficacy. Additionally, a similar CD161-driven exhaustion program is observed in other hematologic malignancies. These findings suggest that targeting the CD161-CLEC2D axis could offer a promising strategy to enhance MM treatment outcomes and CAR-T efficacy. Overall design: We collected BM and PB samples from one relapsed/refractory multiple myeloma (RRMM) patients on the 35th day post-BCMA CAR-T infusion. PBMCs and BMNCs were isolated using density gradient centrifugation with Ficoll. CAR-T cells were sorted based on CD3 and BCMA CAR expression via flow cytometry and subjected to single-cell sequencing