Intestinal epithelial cells (green) are transiently activated and produce MIP-2 (red) during vaginal birth.
Gut cells calmly cohabitate with millions of intestinal bacteria. To avoid constant inflammation, these cells must learn to ignore or tolerate the immune-activating structures (such as lipopolysaccharide, or LPS) that protrude from the surface of the bugs. Gut cells are not simply blind to their microbial neighbors—as was once thought—as they express the LPS receptor Toll like receptor (TLR) 4.
This education in tolerance, according to Lotz and colleagues, begins during birth. Intestinal epithelial cells isolated from fetal mice produced inflammatory cytokines in response to LPS stimulation. Cells from newborn mice, by contrast, produced low levels of cytokines without stimulation, but did not respond...
