Suppression of proliferation of purified pretransplant T cells by MDSCs before and after transplantation. Percentage suppression was determined by comparing the percentage of CFSE^lo pretransplant T cells in anti-CD3/anti-CD28 TCB–stimulated cultures with or without the addition of sorted pretransplant (A) or posttransplant (B) MDSCs after 4 or 5 days of coculture, as shown in the representative line graphs of CFSE staining of gated pretransplant CD4⁺ T cells. Mean percentage suppression mediated by sorted MDSCs obtained from patients before and at serial time points after transplantation for CD4⁺ (C) and CD8⁺ (D) T cells. P values were determined by the Mann-Whitney U test of independent means; significance was subsequently determined by 1-way ANOVA, multicomparison analysis with Holm-Sidak correction. Linear regression analyses of the percentage of Lox-1⁺ cells among pmn MDSCs vs percentage suppression of CD4⁺ (E) and CD8⁺ (F) T cells mediated by the MDSCs at all time points. Mean (± standard error of the mean) concentration of IFN-γ (G), IL-2 (H), and ARG-1 (I) in the culture supernatants from T cells alone, T cells plus anti-CD3/anti-CD28 TCBs, T cells plus anti-CD3/anti-CD28 beads plus MDSCs, or MDSCs alone. P values were determined by 1-way ANOVA, Kruskal-Wallis multi-comparison analysis with Dunn’s correction.