Phenotypes of B-lineage cells present in SCID mice repopulated with embryo cell lines.

(A) Stainings of BM, spleen, and peritoneum cell populations are shown for SCID mice injected with 2 representative embryo cell lines. The organs of SCID mice inoculated with PBS and of BALB/c mice are shown as negative and positive controls, respectively. The contour plots show the CD19, B220/6B2, and CD5 Ag expressions (vertical axis) and the IgM^a+ surface levels (horizontal axis). (B) Intracytoplasmic μH stainings were performed after immunomagnetic depletion of sIgM^a+ splenic cells from reconstituted SCID mice, as described in “Materials and methods.” Photomicrographs of IgM^a-depleted populations are stained with rhodamine-labeled goat antimouse IgM (red). Nuclei are counterstained with DAPI (blue). The magnification scales are × 63 and × 100 for left and right photomicrographs, respectively. The samples were analyzed in a Leitz DMRD system. (C) Flow cytometry analyses for intracytoplasmic H chains in the CD19⁺IgM^a−-splenic cells of reconstituted SCID mice. The dot plot at the left shows the reanalysis performed after depletion of IgM^a+ cells by immunomagnetic cell sorting. The boxes define the CD19⁺IgM^a− and CD19⁻IgM^a− populations present in the sample. The right overlaid histograms represent the findings obtained by labeling with a control FITC-sheep antiserum (dotted lines) and a FITC-sheep F(ab)′₂ antimouse Ig(H+L) (continuous lines), in the CD19⁺IgM^a− (upper histogram) and the CD19⁻IgM^a− (lower histogram) cell populations. The numbers represent the percentage of cH⁺cells.