antibody as confirmation of these results. In contrast to X-gal staining, which 
frequently produced a reaction product distributed throughout the cytoplasm, all 
positive cells detected by antibody staining showed a clear concentration of staining 
within the nucleus. The ability to detect p-galactosidase by immunofluorescence 
provided the opportunity to co-localize recombinant gene expression in either basal 
cell (cytokeratin 14) or columnar cell (cytokeratin 18) markers. Figure 9 shows a 
section of lacZ reconstituted xenograft incubated simultaneously with 3 antibodies: 
red-p-galactosidase, blue- cytokeratin 14, and green- cytokeratin 18. Of 1,500 lacZ 
positive cells counted, only 1 colocalized with the basal cell marker. 
Figure 9. Ad5-CMV-lacZ gene transfer to specific cell types of xenograft. 
Recombinant DNA Research, Volume 17 
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