Mucins in Infectious Colitis Figure 8. Induction of MUC1 in human intestinal infection. MUC1 expression in distal colon in humans with S. St Paul (upper left panel) and C. jejuni (3 upper right panels) gastroenteritis (A). The lower panels show lack of MUC1 in non-infected age, sex and colonic site matched controls. The MUC1 quantification scores (B) were higher in colonic biopsies from infected (N) than non-infected (#) patients (* p,0.05, Mann Whitney U test, n = 8). Colonic biopsies from two IBD patients with acute C. difficile infection demonstrated that MUC1 is higher during infection even in the background of chronic inflammation. The photographs were taken using 206 magnification. doi:10.1371/journal.pone.0003952.g008 ulcerative colitis [61]. MUC5AC was not detected in the infected mice in our study, suggesting that induction of MUC5AC may arise from more long term effects of chronic inflammation. However, similar to our findings in murine C. rodentium infection, a reduction in MUC2 expression occurs in UC adjacent to ulceration and in active colitis [62,63], and MUC1 expression was upregulated in severe UC at the site of rupture of crypt abscesses [63]. Our non-infected human biopsies from IBD patients only had a very low amount of MUC1, but they did not contain any crypt abscesses, which may induce MUC1 in a similar manner to acute infection. In conclusion, in response to intestinal infection mucin secretion is increased and most mucins are depleted from the epithelium whilst MUC1 is upregulated. As mucins bind pathogens, increasing the secretion of mucins is likely to aid the host by trapping and removing pathogens from the epithelial surface. Pathogens may subvert this host defence by inhibiting mucin synthesis and secretion or causing premature shedding of the mucus producing epithelial cells. Further exploration of the dynamic host mucin – bacterial interactions that occur in the mucin covered mucosal interface will increase our understanding of human susceptibility to infection. Supporting Information Table S1 Histological scoring of murine colitis. Found at: doi:10.1371/journal.pone.0003952.s001 (0.03 DOC) MB Figure S1 Mild PAS staining with and without prior saponifi- cation on a non-infected and C. rodentium infected mouse. Found at: doi:10.1371/journal.pone.0003952.s002 (7.16 MB TIF) Figure S2 Expression of Muc1 in the distal large intestine is upregulated in response to infection with C. rodentium. Repre- sentative examples of Muc1 expression determined by immuno- histochemistry in the distal colon of mice infected with C. rodentium for 12 days and non-infected mice. The photographs were taken using 206 magnification. Found at: doi:10.1371/journal.pone.0003952.s003 (26.10 MB TIF) PLoS ONE | www.plosone.org 12 December 2008 | Volume 3 | Issue 12 | e3952