Characteristics of the severe adverse effect observed in one mouse after RAG1 gene transfer. Six months after primary transplantation, a mouse moving slower and weighing less than its littermates was killed. (A) Cytologic analysis was performed on spleen cells. May Grünwald-Giemsa staining was performed on cytospin slides. Images were visualized using a Leica DM:RB microscope equipped with a 40 ×/0.7 objective lens and a Leica 350F camera (Leica, Wetzlar, Germany). The total original magnification of the image is × 400. (B) LAM-PCR was performed on the DNA extracted from the enlarged organs and on bone marrow cells from a wild-type C57BL/10 mouse. (C) The hRAG1 copy number was quantified on the DNA extracted from the enlarged organs. (D) hRAG-1 expression was determined on the RNA extracted from bone marrow, liver, and spleen cells and compared with the expression in the spleen and bone marrow of the other RAG1-TM mice. hRAG-1 transcript expression was compared with endogenous acidic ribosomal phosphoprotein expression (PO) and expressed as a percentage of a reference sample (RAG-1 expression in the thymus of a wild-type mouse). Data are expressed as means plus or minus SD.