Figure 3.

Percent T lymphocyte suppression by MDSCs. Immature myeloid cells with the surface markers CD33⁺CD11b⁺HLA-DR^dim were isolated on days 4, 7, 14, and 21 after sepsis, and from healthy control subjects. Autologous T lymphocytes were stimulated with soluble anti-CD3/28 and seeded in a co-culture with MDSCs in a 1:1 ratio. T cells were labeled with CellTrace Violet to detect proliferation, and a proliferation index (PI) was calculated for both CD4⁺ and CD8⁺ T cells using flow cytometric analysis. Percent suppression was calculated as the ratio of PI from stimulated T cells in the presence of MDSCs and the PI of stimulated T cells in culture medium alone. Percent suppression for both CD4⁺ and CD8⁺ T cells was significantly different between day 4 vs. 14 (p = 0.0402 and 0.0012), day 4 vs. 21 (p = 0.0225 and <0.0001), and day 7 vs. 21 (p = 0.037 and 0.045). There was no significance noted of percent suppression of CD4⁺ and CD8⁺ T cells between days 7 and 14 (p = 0.17 and 0.08). This T cell suppression was not seen in age-matched healthy control subjects. Modified from Hollen et al. (62). *indicates statistically significant intervals (p < 0.05).