In these lymphoid tissues, antigens are up taken by M cells in the epithelial layer, and antigen-specific immune responses are subsequently initiated by GALT cells.
This enhanced expression of barrier-protective genes may present an obstacle to invasive gastrointestinal bacteria that seek to invade by paracellular translocation across the epithelial layer, like Vibrio cholera and Clostridium difficile [22].
In a human model of gut ischemia and reperfusion, short-term ischemia induced a strong increase of plasma i-FABP, paralleled by histological damage of the epithelial layer and breakdown of intestinal barrier [ 22].
These results suggest that this strain may be of interest for increasing the intestinal barrier against pathogens, firstly by strengthening the physical resistance of the epithelial layer and secondly by modulating the immune system towards a preactivated steady state.
At 4 5 days after surgery, the epithelial collar of the free connective tissue graft became white and was followed by a gradual desquamation of the epithelial layer.
Certain probiotic strains and multispecies supplements may enhance the expression of mucin components and protect the epithelial layer by adhering to it, thus preventing mucolytic bacteria from digesting the mucus and making the epithelial barrier more vulnerable [ 35].
By 3 days after treatment, the epithelial layer had begun to recover, and the 7-day group showed regeneration of the villi and a restored structural layers including the mucosa, submucosa, and muscularis.
Furthermore, due to its distinctive structure within the body, with the highly vascularized and oxygenated subepithelial mucosa on one side and the severely oxygen deficient lumen on the other side, the gastrointestinal (GI) tract is characterized by a steep oxygen gradient across the epithelial layer [4].
Primary human oral epithelial cells (HOECs) were isolated and expanded in serum free keratinocyte growth medium with supplements as previously described by Krisanaprakornkit et al. Briefly, the epithelial layer was separated from the underlying fibrous connective tissue with dispase.
The decline in goblet cell numbers observed with Gram-negative strains was accompanied by a significant increase in mucin secretion, thus it was postulated that these were related: excessive mucin production exhausted the cells and caused changes in the architecture of the epithelial layer (restored by bifidobacteria).
