Figure 8. CD70 expressed by host hematopoietic APCs suppresses GVHD by inducing AICD in alloreactive donor T cells.

(A) Chimeras were generated between C57BL/6 WT and CD70^-/- mice through syngeneic transplants with 5×10⁶ BM plus 5×10⁶ splenocytes. After 3 months, the chimeric hosts were lethally irradiated with 800 cGy for allo-HCT. Survival data of chimeras receiving 4×10⁶ BALB/c BM ± 3×10⁶ PanT are pooled from two individual experiments (n=7-14 for each group). Statistical significance evaluated by log rank (Mantel-Cox) test. * P<0.05. (B) WT and CD70^-/- BMDCs were cultured in RPMI medium containing GM-CSF for 6 days. LPS was added to culture on day 6 to fully mature the BMDC culture. On day 7 CD70 expression on CD11b⁺CD11c⁺ BMDCs was assessed by flow cytometry. (C) Active caspase-8 was analyzed on day 5 after culture of WT or CD70^-/- BMDCs mixed at a 1:5 ratio with BALB/c PanT cells. Shown are representative data from three experiments. Statistical significance for caspase-8 activation was analyzed by student's t test. **P<0.01; ***P<0.001.