Only the CD62L⁺ subset of CD4⁺CD25⁺ Treg cells protects from lethal aGVHD in vivo. (A) CD4⁺ splenocytes from C57BL/6 donors were sorted into CD4⁺CD25^- (not shown), CD4⁺CD25⁺CD62L⁺, and CD4⁺CD25⁺CD62L^- subpopulations. (B) Lethally irradiated BALB/c recipients received 2 × 10⁶ TCD BM cells from C57BL/6 mice for reconstitution plus 500 000 C57BL/6-derived CD4⁺CD25^- T cells either alone (▪; n = 10) or together with 500 000 CD4⁺CD25⁺CD62L⁺ (▴; n = 10) or CD4⁺CD25⁺CD62L^- (▾; n = 10) Treg cells. Additional groups were injected with TCD BM and 500 000 CD4⁺CD25⁺CD62L⁺ (▵; n = 5) or CD4⁺CD25⁺CD62L^- (▵; n = 3) Treg cells only. Data were pooled from 2 independent experiments.