Figure 4. Siplizumab reduces the percentage of total FoxP3⁺ cells, but expands the fraction of proliferating FoxP3^HI cells and the ratio of proliferating FoxP3⁺ to CD4⁺ and CD8⁺ cells in allogeneic HLA-mismatched MLRs.

Total (A) and proliferating (B) CD4⁺ CD25⁺ CD127⁻ FoxP3⁺ subsets post-MLR at different drug concentrations, back-gated on responder total and proliferating CD3⁺ T cells respectively. FoxP3⁺ cells were further characterized on the basis of CD45RA (+/−) and FoxP3 (hi/lo) expression. (C) Total, non-proliferating (CFSE^HI) and proliferating (CFSE^LO) CD4⁺ CD25⁺ CD127⁻ FoxP3⁺ cells represented as percentage of total, non-proliferating and proliferating CD3⁺ T cells respectively (median [IQR]); n = 10 unique donor pairs. (D) Ratios of proliferating (CFSE^LO) CD4⁺ CD25⁺ CD127⁻ FoxP3⁺ cells to either CFSE^LO CD4⁺ or CFSE^LO CD8⁺ cells, and ratio of CFSE^LO CD45RA⁻ FoxP3^HI/LO subsets to CFSE^LO CD4⁺ cells (median [IQR]); n = 10 unique donor pairs. Red-colored symbol: p < 0.05 compared to No drug MLR (repeated-measures ANOVA and Dunnet’s multiple comparisons test, or Friedman’s test and Dunn’s multiple comparisons tests, as appropriate).