Figure 4.

Inducible T-cell co-stimulator (ICOS) is indispensable for regulatory T cells (Tregs) survival and homeostasis in chronic graft-versus-host disease. Lethally irradiated BALB/c mice were transplanted with 0.25 × 10⁶ CD25⁻SPLs and 5 × 10⁶ T-cell-depleted bone marrow from Cre⁻ICOS^fl/fl or Foxp3^CreICOS^fl/fl mice on B6 background. Body weight and clinical score (A) were monitored weekly, n = 6–8 mice/group. Spleens were harvested at day 60 after bone marrow transplantation (BMT) and subjected to FACS staining. Representative flow images from individual mice and mean percentage of Foxp3 gated on H-2K^b+CD4⁺ T cells and live/dead gated on H-2K^b+CD4⁺ Foxp3⁺ are shown (B). Representative dot plots from individual mice and dot graphs of mean percentage of CD44^hiCD62L^lo and CD44^loCD62L^hi gated on H2K^b+CD4⁺Foxp3⁺ T cells are shown (C). n = 4–5 mice/group. *p < 0.05, **p < 0.01, and ***p < 0.001.