Localization of adenovirus-expressed recombinant protein in arthritic mouse paws. Two DBA/1 mice were immunized with type II collagen/complete Freund's adjuvant and one week later injected intra-articularly (into hind ankles) with 10 μl containing 10× 7 total plaque forming units adenoviral particles encoding Lac-Z. The animals were sacrificed 48 hours later and the tissues photographed using a reverse phase microscope (50×). In the upper panel, the tissues were incubated with beta galactosidase substrate. The majority of the cells containing Lac-Z (upper panel, stained blue) appear to be fibroblast-like synoviocytes lining the surface of the synovium, although staining can also be detected in monocyte-like synoviocytes. The uninjected hindpaws were used as controls for each animal (lower panel). The data shown are representative of data obtained by analyzing multiple sections of each hindpaw.