Figure 4. Suppressive activity of regulatory T cells developing in humanized mice is comparable to that of normal human donors.

Panel (A) shows a representative phenotypic profile and purity of CD4⁺CD25⁻ (responders, left) and CD4⁺CD25⁺CD127⁻ (suppressors, middle) T cells of a humanized mouse after FACS sorting. The frequency of CD25⁺CD127⁻ cells among gated CD4 single positive T cells in each cell fraction is shown. Right panel shows intracellular FoxP3 expression of the indicated fraction. The shaded line represents the staining with isotype control mAb and the thick line and dashed line represent the test staining of suppressor and responder cells, respectively. (B and C) In vitro suppression of proliferation of CD4⁺CD25⁻ T cells (responders) by FACS-sorted CD4⁺CD25⁺CD127⁻T cells (suppressors) isolated from normal human PBMCs or pooled spleen and lymph nodes of humanized mice 20 wks post-transplantation. CD4⁺CD25⁻ T cells (2×10⁴) isolated from human PBMC or pooled spleen and LN cells of 3 humanized mice were incubated with syngeneic CD4⁺CD25⁺CD127⁻ T cells in indicated ratios in the presence of plate-bound anti-CD3 mAb (1 μg/ml) and soluble anti-CD28 mAb (2.5 μg/ml) for 4 days (B) or in the presence of 30Gy-irradiated allogeneic PBMC as stimulators for 5 days (C). Cultures were pulsed with [³H]thymidine at day 3 (B) or 4 (C) and harvested 16 h later. Data are expressed as mean of triplicates.