O24 – Invariant Natural Killer T-cells modulate the Gamma-Delta-Lymphocyte response to polymicrobial sepsis

Author(s):

Whitney Young, John Young, Mai Tran, Shiang Chung, William Cioffi, Alfred Ayala, Daithi Heffernan, Brown University, Rhode Island Hospital

Background: Lymphocytes and specifically Innate Lymphocytes Cell subpopulations (ILCs) are emerging as central mediators in the response to and survival from sepsis. We have recently shown that among these ILCs, Invariant Natural Killer T-cells (iNKT-cells) are key to survival from sepsis, and are critical modulators of neutrophil and macrophage function.
Recent evidence suggests iNKT-cells may be capable of affecting other ILCs including the gamma-delta-T-cells (GDT-cell). Sepsis is associated with a divergent response; a preservation of iNKT-cells and a loss of GDT-cells in humans. .

Hypothesis: Sepsis will induce significant altertions in GDT-cell responses in a variety of tissue compartments, a response modulated by iNKT-cells.

Methods: Both male wild type (WT) and iNKT-cell -/- mice underwent cecal ligation and puncture or sham. Liver, blood, and peritoneal fluid cell populations and circulating cytokines were assessed at 24 hours. Monoclonal antibodies directed against CD3, TCR-pan-δΔ (GDT-cells), and Vα18-TCR were used. GDT-cell activation was evaluated using surface expression of CD69 and circulating levels of IL-17

Results: Following sepsis, wt and iNKT-/- mice displayed decreased circulating hepatic and peritoneal CD3+lymphocytes. Sepsis was associated with increased hepatic GDT-cells in wt (1.64 vs 1.33 x10^4;p=0.04) which were more activated (47% vs 23%;p=0.01). Further, in wt mice, sepsis was noted to induce an increase in absolute number of circulating GDT-cells (144 vs 89/100microL;p=0.02). Following sepsis, peritoneal GDT-cells were also increased (86.6×10^4 vs 4.08×10^4;p<0.01) and more activated (78% vs 17%;p<0.01). Conversely, iNKT-/- mice displayed decreased hepatic GDT-cells following sepsis (2.03 vs 4.02×10^4;p<0.01) with lower activation (17% vs 32%;p<0.01). This was associated with a decrease in peritoneal GDT-cells following sepsis in iNKT-/-mice (1.47 vs 3.01×10^4;p=0.03). Compared to wt mice, iNKT-/-mice had markedly lower IL-17 levels (2.73 vs 12.12 pg/ml;p<0.01).

Conclusions: Sepsis induces priming and activation of GDT-cells in a variety of tissue sources. We demonstrate that iNKT-/- mice have the ability to alter sepsis induced changes in the GDT-cell tissue populations and IL-17 expression. This data supports our previous observation of a divergent role of ILCs in human sepsis. ]iNKT-cells may play a functional role in mediating the ILC response to sepsis.