MKI67 and infection: Photomicrographs reepresentative for four independent experiments illustrate the average numbers of (A) apoptotic epithelial cells (Casp3+), (B) proliferating epithelial cells (Ki67+), (C) T lymphocytes (CD3+), and (D) B lymphocytes (B220+) in at least six high power fields (HPF) as quantitatively assessed in ileal paraffin sections applying in situ immunohistochemistry at day 6 post-infection (A: 400× magnification, scale bar 20 μm; B–D: 100× magnification, scale bar 100 μm).