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Published on: May 22, 2020
Assessment of T Cell Receptor Complex Expression Kinetics in Natural Killer Cells
Khder H Rasul1,2, Alamdar Hussain1, Hazel Reilly1
1Center for Hematology and Regenerative Medicine (HERM), Department of Medicine Huddinge, Karolinska Institutet, SE-141 83 Stockholm, Sweden.
Abstract:
Among the polypeptides that comprise the T cell receptor (TCR), only CD3ζ is found in Natural Killer (NK) cells, where it transmits signals from activating receptors such as CD16 and NKp46. NK cells are potent immune cells that recognize target cells through germline-encoded activating and inhibitory receptors. Genetic engineering of NK cells enables tumor-specific antigen recognition and, thus, has a significant promise in adoptive cell therapy. Ectopic expression of engineered TCR components in T cells leads to mispairing with the endogenous components, making a knockout of the endogenous TCR necessary. To circumvent the mispairing of TCRs or the need for knockout technologies, TCR complex expression has been studied in NK cells. In the current study, we explored the cellular processing of the TCR complex in NK cells. We observed that in the absence of CD3 subunits, the TCR was not expressed on the surface of NK cells and vice versa. Moreover, a progressive increase in surface expression of TCR between day three and day seven was observed after transduction. Interestingly, the TCR complex expression in NK92 cells was enhanced with a proteasome inhibitor (bortezomib) but not a lysosomal inhibitor (chloroquine). Additionally, we observed that the TCR complex was functional in NK92 cells as measured by estimating CD107a as a degranulation marker, IFNγ cytokine production, and killing assays. NK92 cells strongly degranulated when CD3ε was engaged in the presence of TCR, but not when only CD3 was overexpressed. Therefore, our findings encourage further investigation to unravel the mechanisms that prevent the surface expression of the TCR complex.
Insights
Natural Killer (NK) cells can express the T cell receptor (TCR) complex, but surface expression requires specific CD3 subunits. Proteasome inhibition enhances TCR complex expression in NK92 cells, suggesting potential for adoptive cell therapy.
Area of Science:
- Immunology
- Cell Biology
Background:
- Natural Killer (NK) cells are crucial immune cells utilizing germline-encoded receptors for target recognition.
- Genetic engineering of NK cells offers promise for adoptive cell therapy, enabling tumor-specific antigen recognition.
- T cell receptor (TCR) expression in T cells can cause mispairing with endogenous components, necessitating knockout strategies.
Purpose of the Study:
- To investigate the cellular processing and surface expression of the T cell receptor (TCR) complex in Natural Killer (NK) cells.
- To determine the functional capacity of the TCR complex when expressed in NK cells.
- To explore strategies for enhancing TCR complex surface expression in NK cells.
Main Methods:
- Exploration of TCR complex cellular processing in NK cells.
- Assessment of surface expression of TCR and CD3 subunits.
- Treatment of NK92 cells with proteasome (bortezomib) and lysosomal (chloroquine) inhibitors.
- Functional assays including CD107a degranulation marker, Interferon-gamma (IFNγ) production, and killing assays.
Main Results:
- Surface expression of the TCR complex in NK cells was dependent on the presence of CD3 subunits.
- Progressive increase in surface TCR expression was observed between day three and seven post-transduction.
- Proteasome inhibitor bortezomib enhanced TCR complex expression in NK92 cells, while lysosomal inhibitor chloroquine did not.
- The TCR complex was functional in NK92 cells, evidenced by degranulation, IFNγ production, and killing activity.
Conclusions:
- The study elucidates the cellular processing of the TCR complex in NK cells.
- Findings suggest that proteasomal degradation may limit TCR complex surface expression in NK cells.
- The functional expression of the TCR complex in NK92 cells supports its potential utility in engineered immunotherapies.
- Further research is warranted to understand and overcome the mechanisms limiting TCR complex surface expression in NK cells.
