[1] Genentech Inc, Dept Pathol, S San Francisco, CA 94080 USA
[2] Genentech Inc, Dept Immunol, S San Francisco, CA 94080 USA
[3] Univ Glasgow, Western Infirm, Dept Pathol, Glasgow G11 6NT, Lanark, Scotland
[4] Western Infirm, Gastroenterol Unit, Glasgow G11 6NT, Lanark, Scotland
[5] Royal Free Hampstead NHS Trust, Dept Histopathol, London NW3 2QG, England
[6] Univ Calif San Francisco, Dept Pathol, San Francisco, CA 94143 USA