Immunity & infection
CD38 is an ectonucleotidase which degrades nicotinamide adenine dinucleotide (NAD). We found a negative correlation between CD38 expression on CD8 T cells and infections in patients with SLE. We sought to determine whether CD38 is responsible for the decreased cytotoxicity of CD8 T cells in SLE.
We used sorted human primary CD8 T cells, TALL-104 and CRISPR-generated CD38-deficient Jurkat cells. 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.
Compared with CD38low, CD38high CD8 T cells displayed lower cytotoxicity as determined by the expression of CD107a, granzyme B, perforin and IFNg. Eomes and T-bet, which regulate cytotoxic function of CD8 T cells, were decreased in CD38highCD8 T cells. CD38 suppressed the activity of the NAD-dependent deacetylase Sirt1. CD38high CD8 cells had lower NAD and higher acetylation level on lysine residues and stabilized expression of EZH2 which is known to repress Eomes and T-bet. Finally, overexpression of CD38 in CD38lowCD8 T cells or TALL-104 cells increased acetylated protein and decreased cytotoxicity against P815 cells.