Figure 1.
The epithelial barrier is comprised of a single layer of epithelial cells intertwined by tight junctions.
The mechanical barrier is increased further by a mucus layer. Binding of bacteria to TLRs present on epithelial cells results in the activation of NFκB, ultimately resulting in the release of pro-inflammatory and anti-inflammatory cytokines. After phagocytosis, bacterial products are internalized and then are recognized by receptors of the NOD family (NLRs), resulting in the modulation of the inflammatory response. Dendritic cells are capable of internalizing bacteria sampled from the lumen, after which bacteria are presented to immune effector cells. HSPs, heat shock proteins; NLR, NOD-like receptor; sIgA, secretory immunoglobulin A; TLR, Toll-like receptor.
Figure 2.
The resident microbiota interferes in the process of mucositis.
Depicted are five possible ways in which intestinal bacteria can attenuate or aggrevate mucositis: 1) influencing the inflammatory process, 2) influencing intestinal permeability, 3) influencing the composition of the mucus layer, 4) influencing resistance to harmful stimuli and enhancing epithelial repair, and finally, 5) the activation and release of immune effector molecules.