Barrier Compartments

Barrier Functions

Functional & Cellular Elements

Mucins

1

Cover, Capture, Deflect, Remove

Loose Mucin labyrinth, sterile dense Adherent Mucin, Mucin Transient

2

Neutralize and Preserve

Neutralize using IgA, anti-microbial agents, detached transmembrane mucin; Preserve epithelium using trefoil factors (TFF1,TFF2,TFF3)

Single Cell Epithelium

3

Antigen & non-antigen Surveillance, Detection, Barrier lubrication & Sustenance

Sample surveillance by αβ-IEL, δγ-IEL, M-cells, dendritic cells, goblet cells; detect mucin disturbance by epithelial transmembrane mucin; lubricate and sustain epithelium by Globlet cells producing mucin, trefoil factors; tuft cells and enteroendocrine cells.

4

Cap and Close off Luminal Contents

Epithelial Cells with toll-like receptors, tight junctions, epithelial cytokine production, apical transmembrane mucin & cytosol signaling, basolateral growth factors

Lamina Propria and Submucosa

to Subserosa

5

Pre-emptive Immune Actions

Innate Immune Cells (ILC) - Class I, II, III interacting with epithelial cells, IEL’s, Globlet cells, Dendritic cells, M-Cells

6

Adaptive Counter-Attack Immune Actions

Monocytes, Macrophages, Mast Cells, B- Lymphocytes, T-Lymphocytes, inflammosome formation

7

Host Warning and Eliminate Effluent

Enteric glial neurons with 2 classes of voltage-gated receptors (ASIC, TRPV) on afferent neurons, with input to efferent neurons that are responsive to cytokine secretions from IEL, epithelial cells, mast cells and ILC’s; these neurons extend from the epithelial cell layer (including tuft cells and enteroendocrine cells) downward into the submucosal plexus and myenteric plexus, with functions for sensory, epithelial, vascular, pain, nausea, emesis and motility.

IEL- intra-epithelial lymphocytes; ILC- Immune Lymphoid Cells; ASIC- acid sensing ion channels; TFF- trefoil factors; TRPV- transient receptor potential vanilloid