Figure 6.

Postnatal MSI mucus layer maturation correlates with increased resistance to E. coli K1 systemic infection. (a) Confocal micrographs of Methacarn-fixed MSI tissue sections from neonates at P2 and P9; sections stained for Muc2 (green) and DNA (grey). (b) SEM of neonatal MSI tissue obtained at P2 and P9; right panels show magnification of inset yellow boxes in left panels. (c) Ex-vivo quantification of MSI mucus layer and villus height from P2-P11; n = 4 animals, mean ± SEM. (d) Correlation between MSI villus exposure (proportion of villus not covered by mucus layer) and survival between P2-P9 after initiation of E. coli A192PP colonization at P2; n = 4 animals, mean ± SEM, linear regression of data indicated by red dashed line. (e) Confocal z-plane projection of fluorescently labelled ex-vivo MSI tissue overlaid with fluorescent beads; representative 3D projection (left panel) and x/z-axis cross-sections from P2 and P9 tissues (right panels; yellow box) shown; labelled tissue (blue), fluorescent beads (red). (f) Quantification of z-axis bead distribution in mucus of MSI tissue from P2 and P9 neonates; data from confocal z-plane projections as shown in (e); error bars are SEM from n = 4 animals, mean ± SEM (thin lines); approximate positions of the villus base and tip along the z-axis are indicated (dashed lines).