NK Clusters

"While these clusters shared high Siglec-9 expression, they displayed distinct activating receptor profiles: NKp30 was highly expressed in clusters 2 and 8, whereas DNAM-1 (CD226) and NKp46 were elevated in clusters 8 and 9. Furthermore, clusters 8 and 9 were specifically enriched with molecules associated with cytotoxic function, including CD161, Siglec-7, CRTAM, NKG2D, and perforin, suggesting these subsets are primed with both activating receptors and cytolytic machinery. Interestingly, cluster 2 was also enriched in the CD107a/b⁺ fraction despite exhibiting lower levels of classical activating receptors. This suggests that cluster 2 may represent a functionally distinct NK subset with lower intrinsic cytotoxic potential, specialized instead for antibody-dependent viral clearance. This interpretation aligns with our previous observations. Notably, the expression profiles of these ADCC-responsive NK subsets closely resemble the cytotoxic signatures reported in NK cells from HIV elite controllers, suggesting a conserved effector program may underpin natural antiviral immunity. To investigate the ADCC responses in vivo, we examined the expression of ADCC-related genes in the spatial transcriptomics of SARS-CoV-2-infected mice with 5SB12 mAb pretreatment. Similar to human NK cells, Siglece, the mouse homolog of Siglec-9, was highly expressed in the VCs associated with the +/+ treatment group, including VCs 2, 8, 4, 9, and 12. Multiple ADCC-related or NK cell activation genes, including Tyrobp, Prf1, Klrb1c, Slamf6, and Sh2d1a, were highly expressed in the NK cell-enriched VCs 4, 9, and 18. Notably, Gzmb was upregulated in both VC4 and VC9, encoding granzyme B, which induces apoptosis of targeted cells. This supports that the presence of an ADCC-inducing antibody promotes the activation of NK cells with low cytotoxicity in vivo in response to SARS-CoV-2 infection."