Figure 4.

Histological features of the bovine xenografts. a shows an H&E-stained section of adult bovine skin. c, e, and f show an H&E-stained section from a bovine fibropapilloma. The sections shown in b, d, f, and h are from bovine organotypic raft/xenografts. The control graft shown in b was generated with uninfected bovine keratinocytes and BALB fibroblasts. The graft shown in d, f, and h was generated with BPV-1-infected keratinocytes, and the dermal equivalent of this graft contained BALB/BPV fibroblasts that resulted in a fibroma. Characteristic features of papillomavirus infection are indicated with arrows: acanthosis (a); koilocytosis (ky); prominent keratohyalin granules (g); parakeratosis (pk); and hyperkeratosis (hk). Flanking mouse skin (ms) is shown in b. Magnifications are indicated.