Analysis of FA-D2 and unidentified downstream group FA cells. (A) FANCD2 immunoblots detect the FA-D2 group. (i) No FANCD2 protein was observed at normal exposure of the immunoblot in sample EGFA014-L (top arrow). Long exposure revealed 2 barely detectable FANCD2 bands (bottom arrow), indicating residual levels of the FANCD2 protein, as previously shown in the reference D2 cell line PD20.^6,10  Ponceau S staining is shown as loading control. Sequencing data further confirmed mutations in the FANCD2 gene in this patient (A.S., data not shown). (ii) FANCD2 immunoblot of PHA-stimulated primary fibroblasts and EBV-immortalized cells from FA-D2 patient EGFA021. (B, i) Unidentified group patients EGFA006 and EGFA053 have normal FANCD2 patterns in both their primary fibroblasts and lymphocytes (EGFA053-L; not shown). (ii) BRCA2 and NBS1 immunoblots detected no abnormalities in the fibroblasts of these 2 patients. EUFA243 and EUFA1020 EBV cell lines were used as positive controls for BRCA2 and NBS1 deficiency, as indicated.