Figure 1.

Inducible T-cell co-stimulator (ICOS) contributes to the progression of chronic graft-versus-host disease (cGVHD). (A) Lethally irradiated BALB/c mice were transplanted with 5 × 10⁶ T-cell-depleted bone marrow (TCD-BM) or plus 0.5 × 10⁶ whole SPLs from wild-type (WT) B6 mice. Spleens were processed and analyzed by flow cytometry. Mean fluorescence intensity (MFI) of ICOS on gated donor CD4, CD8, and regulatory T cells (Tregs) are shown, n = 3–5 mice/group. BALB/c mice were lethally irradiated and transferred with 0.25 × 10⁶ CD25⁻SPLs and 5 × 10⁶ TCD-BM from WT or ICOS^−/− mice on B6 background. Body weight (B) and clinical scores (C) of cGVHD were monitored bi-weekly for 50 days, n = 8 mice/group. Recipient skin and lung were harvested at day 60 after bone marrow transplantation (BMT) and processed for Masson’s trichrome staining. Representative images from one experiment are shown (D). (E) Collagen deposition of skin and lung was qualified by ImageJ as the ratio of collagen area to the whole area of tissue, n = 4 mice/group. *p < 0.05 and **p < 0.01.