Identification of Human Immune Cell Subtypes Most Vulnerable to IL-1ß-induced Inflammatory Signaling Using Mass Cytometry

Hema Kothari; Corey M. Williams; Chantel McSkimming; Mythili Vigneshwar; Eli R. Zunder; Coleen A. McNamara

As IL-1β signals through binding to its surface receptor IL-1R1, we reasoned that the memory T cells that show induced expression of p-NF-kB or p-p38 upon IL-1β stimulation express IL-1R1 while the remaining memory T cells do not. However, mean expression of IL-1R1 was significantly lower in the p-NF-kB + memory T cells in comparison to the p-NF-kBmemory T cells (Fig. 3a) . IL-1β signaling can induce receptor internalization 30 yet, there was no reduction in the mean expression of surface IL-1R1 after 15 minutes of IL-1β stimulation in both the p-NF-kBand p-NF-kB + memory T cell subsets ( Fig. 3a) . Cell surface IL-1R2 binds to IL-1β but acts as a decoy receptor 31 . As such, the ratio of the levels of IL-1R1 and IL-1R2 on the cell surface may determine the signaling outcome induced by IL-1β. Therefore, we also analyzed expression of IL-1R2 on the p-NF-kB + and p-NF-kBmemory T cells. IL-1R2 expression could not be detected on T cells or any other immune cell type in both vehicle-treated and IL-1β-stimulated PBMCs. Notably, the same IL-1R2 antibody clone measured IL-1R2 expression on CD4 memory T cells activated with anti-CD3, anti-CD28 and IL-2 for 48 hours. Unstimulated cells in culture also showed moderate levels of IL-1R2 expression, yet it was undetectable on unstimulated freshly purified PBMCs (Supplementary Fig. 8) .