Targeting of the CD161 Inhibitory Receptor Enhances Bone Marrow-Resident Memory CD8+ T Cell-mediated Immunity Against Multiple Myeloma [Mice RNA-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: The 5TGM1 MM model was established by intravenously injecting luciferase-expressing 5TGM1 cells (1×106 cells in 200 µL PBS) into C57BL/KaLwRij mice. On week 5 post-tumor injection, mice exhibiting increased bioluminescence signals were randomized into two treatment cohorts: an isotype control antibody group and an anti-NK1.1 monoclonal antibody (mAb) group.Antibodies were administered via intraperitoneal injection (5 mg/kg) twice per week. On day 14 post-antibody administration, BM single-cell suspensions were collected, and CD8a+ T cells were isolated using the CD8a+ T Cell Isolation Kit , total RNA was extracted using the RNA rapid extraction kit for RNA sequencing.