FA chimeras exhibit increased GVHD-inducing potential. (A) Survival of secondary BM transplanted chimeras. 5 × 10⁶ BMCs plus 5 × 10⁶ splenocytes from WT C57BL/6 mice (B6, H-2^b+, CD45.2⁺) or 10 × 10⁶ WBMCs plus 5 × 10⁶ splenocytes from Fanca^−/− (left) or Fancd2^−/− (right) mice (C57BL/6: B6, H-2^b+, CD45.2⁺) were transplanted to lethally irradiated Boy J recipients (C57BL/6: B6, H-2^b+, CD45.1⁺). Donor-derived chimera (CD45.2⁺) were assessed at 4 months after BMT. The recipients with greater than 95% donor-derived chimera were then subjected to 2nd BMT by 9 Gy irradiation and injecting 5 × 10⁶ BM cells along with 2 × 10⁶ T cells isolated from either B6 (syngeneic; H-2^b+, CD45.2⁺) or Balb/c (allogeneic; H-2^d+, CD45.2⁺) mice. Survival of the mice was monitored by Kaplan-Meier curve method. (B) Histopathologic examination of GVHD target organs. Tissue sections (skin, liver, lung, and small intestine) were stained with hematoxylin and eosin and examined by microscope. Asterisks show lymphocytic infiltrates; green arrows show tissue destruction; black arrows show focal alveolar hemorrhages in lung. The specimens shown are representative images of 5 mice in each group with similar histologic features. (C) GVHD clinical scores were determined as a measure of GVHD severity on days 14 and 21 after allogeneic BMT. Data are presented as means plus or minus SD of 2 independent experiments (n = 7 to 10 per group). (D) Weight loss of the recipients. Average weights are shown for mice described in (A). Data are presented as means plus or minus SD of 2 independent experiments (n = 7 to 10 per group).