Background/Purpose: CD38 is an ectonucleotidase that has the ability to degrade nicotinamide adenine dinucleotide (NAD). The percentage of CD38 expressing CD8 T cells are increased in patients with SLE in whom cytotoxic responses are known to be decreased. We sought to determine whether CD38 is responsible for the decreased cytotoxicity in T cells from patients with SLE.

Methods:

We used sorted human primary CD8 T cells, TALL-104 and CRISPR-generated CD38 knock out Jurkat cells. Electroporation was performed using Amaxa. Cells were stimulated with anti-CD3/CD28 or P815 cells. Degranulation and cytotoxicity were assayed by flow cytometry (FCM). Expression of cytolytic molecules (granzymeB, perforin and IFN-g) and the transcription factors Eomes, T-bet and EZH2 were measured by FCM and qPCR. NAD production and protein acetylation were measured using colorimetric or Western blot techniques.

Results:

Compared with CD38^low, CD38^highCD8 T cells displayed lower cytotoxicity as determined by the expression of CD107a, granzymeB, perforin and IFNg. In addition, CD38^highCD8 T cells showed lower cytotoxicity against P815 cells. Eomes and T-bet, which regulate cytotoxic function of CD8 T cells, were decreased in CD38^highCD8 T cells, while EZH2 levels were increased. EZH2 known to repress Eomes and T-bet has been reported to have a higher suppressive capacity and stability when acetylated. SIRT1 is a NAD-dependent deacetylase and controls EZH2 acetylation. Consequent upon lower production of NAD, the levels of proteins acetylated on lysine residues increased in CD38^highCD8 T cells. Lower deacetylation activity of SIRT1 may cause higher acetylation of EZH2 and suppression of Eomes and T-bet in CD38^highCD8 T cells. Finally, overexpression of CD38 in CD38^lowCD8 T cells or TALL-104 cells increased acetylated protein and decreased degranulation and cytotoxicity against P815 cells, which indicates that CD38 may reprogram cytotoxicity in CD8 T cells.

Conclusion: We present novel evidence that CD38^highCD8 T cells which are expanded in patients with SLE display decreased cytotoxicity. CD38 causes decreased NAD levels, higher acetylation of EZH2 and subsequent decrease of the cytotoxicity-linked transcription factors, Eomes and T-bet. Our data document the role of CD38 in the control of the cytotoxic response of CD8 T cells and provide a molecular explanation for the known decreased cytotoxic responses in patients with SLE.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/high-level-of-cd38-expression-in-sle-cd8-t-cells-dictates-decreased-cytotoxicity/