Phenotypic and Functional Plasticity of CXCR6+ Peripheral Blood NK Cells
Laura S Angelo1, Graham D Hogg1, Shawn Abeynaike2
1Center for Human Immunobiology, Department of Pediatrics, Texas Children's Hospital, Houston, TX, United States.
Insights
Human natural killer (NK) cells expressing C-X-C-motif-chemokine-receptor-6 (CXCR6) exhibit distinct functions. Expanded CXCR6+ NK cells show enhanced antibody-dependent cellular cytotoxicity (ADCC), suggesting potential for improved cell-based therapies.
Area of Science:
- Immunology
- Cell Biology
Background:
- Human natural killer (NK) cells possess diverse subsets with largely uncharacterized functions.
- C-X-C-motif-chemokine-receptor-6 (CXCR6) marks phenotypically immature, tissue-resident NK cells in mice and humans, with a small subset also found in peripheral blood (PB).
- Conflicting reports exist regarding the phenotypic and functional plasticity of CXCR6+ NK cells.
Purpose of the Study:
- To isolate, expand, and compare the phenotype and function of CXCR6+ and CXCR6- peripheral blood NK (PB-NK) cells.
- To contrast these findings with bulk liver and spleen NK cells.
- To evaluate the potential of specific NK cell subsets for therapeutic applications.
Main Methods:
- Isolation and 14-day *in vitro* expansion of CXCR6+ and CXCR6- PB-NK cells.
- Phenotypic analysis including CD16 and Eomesodermin (Eomes) expression.
- Functional assessment of antibody-dependent cellular cytotoxicity (ADCC).
- Cytokine stimulation (IL-15, IL-2) and STAT-5 phosphorylation analysis in liver, spleen, and PB-NK cells.
Main Results:
- CXCR6+ and CXCR6- PB-NK cells maintained distinct phenotypes after 14 days of expansion.
- Phenotypically immature CXCR6+ PB-NK cells acquired functional equivalence to CXCR6- PB-NK cells post-expansion.
- Day 14 CXCR6+ PB-NK cells demonstrated superior ADCC compared to CXCR6- PB-NK cells, despite reduced CD16 and increased Eomes expression.
- Liver NK cells responded to IL-15 but not IL-2, while splenic and PB-NK cells responded to both.
Conclusions:
- CXCR6+ and CXCR6- PB-NK cells exhibit distinct characteristics and functional potential.
- Expanded CXCR6+ NK cells possess enhanced ADCC capabilities, indicating their therapeutic promise.
- Differential cytokine responsiveness of NK cell subsets highlights tissue-specific functions and potential for targeted therapies.
Abstract:
Human NK cells are comprised of phenotypic subsets, whose potentially unique functions remain largely unexplored. C-X-C-motif-chemokine-receptor-6 (CXCR6) NK cells have been identified as phenotypically immature tissue-resident NK cells in mice and humans. A small fraction of peripheral blood (PB)-NK cells also expresses CXCR6. However, prior reports about their phenotypic and functional plasticity are conflicting. In this study, we isolated, expanded, and phenotypically and functionally evaluated CXCR6+ and CXCR6- PB-NK cells, and contrasted results to bulk liver and spleen NK cells. We found that CXCR6+ and CXCR6- PB-NK cells preserved their distinct phenotypic profiles throughout 14 days of in vitro expansion ("day 14"), after which phenotypically immature CXCR6+ PB-NK cells became functionally equivalent to CXCR6- PB-NK cells. Despite a consistent reduction in CD16 expression and enhanced expression of the transcription factor Eomesodermin (Eomes), day 14 CXCR6+ PB-NK cells had superior antibody-dependent cellular cytotoxicity (ADCC) compared to CXCR6- PB-NK cells. Further, bulk liver NK cells responded to IL-15, but not IL-2 stimulation, with STAT-5 phosphorylation. In contrast, bulk splenic and PB-NK cells robustly responded to both cytokines. Our findings may allow for the selection of superior NK cell subsets for infusion products increasingly used to treat human diseases.
