The human intestinal epithelium is formed by a single layer of epithelial cells that separates the intestinal lumen from the underlying lamina propria. The space between these cells is sealed by tight junctions (TJ), which regulate the permeability of the intestinal barrier. TJ are complex protein structures comprised of transmembrane proteins, which interact with the actin cytoskeleton via plaque proteins. Signaling pathways involved in the assembly, disassembly, and maintenance of TJ are controlled by a number of signaling molecules, such as protein kinase C, mitogen-activated protein kinases, myosin light chain kinase, and Rho GTPases. The intestinal barrier is a complex environment exposed to many dietary components and many commensal bacteria. Studies have shown that the intestinal bacteria target various intracellular pathways, change the expression and distribution of TJ proteins, and thereby regulate intestinal barrier function. The presence of some commensal and probiotic strains leads to an increase in TJ proteins at the cell boundaries and in some cases prevents or reverses the adverse effects of pathogens. Various dietary components are also known to regulate epithelial permeability by modifying expression and localization of TJ proteins.

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Regulation of Tight Junction Permeability by Intestinal Bacteria and Dietary Components

Stability engineering of antibody single-chain Fv fragments.

Immunoglobulins form an important component of the immunological activity found in milk and colostrum. They are central to the immunological link that occurs when the mother transfers passive immunity to the offspring. The mechanism of transfer varies among mammalian species. Cattle provide a readily available immune rich colostrum and milk in large quantities, making those secretions important potential sources of immune products that may benefit humans. Immune milk is a term used to describe a range of products of the bovine mammary gland that have been tested against several human diseases. The use of colostrum or milk as a source of immunoglobulins, whether intended for the neonate of the species producing the secretion or for a different species, can be viewed in the context of the types of immunoglobulins in the secretion, the mechanisms by which the immunoglobulins are secreted, and the mechanisms by which the neonate or adult consuming the milk then gains immunological benefit. The stability of immunoglobulins as they undergo processing in the milk, or undergo digestion in the intestine, is an additional consideration for evaluating the value of milk immunoglobulins. This review summarizes the fundamental knowledge of immunoglobulins found in colostrum, milk, and immune milk.

https://www.mdpi.com/2072-6643/3/4/442/pdf

Perspectives on Immunoglobulins in Colostrum and Milk

The production of antibodies (Abs) in chickens and the extraction of specific Abs from egg yolk (IgY Abs) are increasingly attracting the interest of the scientific community, as demonstrated by th...

Chicken Egg Yolk Antibodies (IgY-technology): A Review of Progress in Production and Use in Research and Human and Veterinary Medicine:

Some of the food-derived tripeptides with angiotensin converting enzyme (ACE)-inhibitory activity have been reported to be hypotensive after being orally administered. The mechanism for the intestinal transport of these tripeptides was studied by using monolayer-cultured human intestinal Caco-2 cells which express many enterocyte-like functions including the peptide transporter (PepT1)-mediated transport system. Val-Pro-Pro, an ACE-inhibitory peptide from fermented milk, was used as a model tripeptide. A significant amount of intact Val-Pro-Pro was transported across the Caco-2 cell monolayer. This transport was hardly inhibited by a competitive substrate for PepT1. Since no intact Val-Pro-Pro was detected in the cells, Val-Pro-Pro apically taken by Caco-2 cells via PepT1 was likely to have been quickly hydrolyzed by intracellular peptidases, producing free Val and Pro. These findings suggest that PepT1-mediated transport was not involved in the transepithelial transport of intact Val-Pro-Pro. Paracellular diffusion is suggested to have been the main mechanism for the transport of intact Val-Pro-Pro across the Caco-2 cell monolayer.

/pdf/transepithelial-transport-of-the-bioactive-tripeptide-val-1kcngo1c43.pdf

Transepithelial Transport of the Bioactive Tripeptide, Val-Pro-Pro, in Human Intestinal Caco-2 Cell Monolayers

Molecular stability of chicken egg yolk immunoglobulin G (IgY) and that of rabbit IgG were compared by measuring antibody activities and conformational changes Stability of rabbit IgG to acid denaturation was much higher than that of IgY Conformation of the IgY molecule was readily changed in acidic conditions, resulting in a rapid loss of antibody activity Much less stable natures of IgY to heat-treatment and guanidine-HCl denaturation than rabbit IgG were also observed Differences in the structure between the two immunoglobulins that might participate in their different stability were inferred from their amino acid sequence data Importance of the intramolecular disulfide linkage in the rabbit light chain and some other structural differences were suggested

Molecular Stability of Chicken and Rabbit Immunoglobulin G

Encapsulation of antibodies isolated from chicken egg yolk (IgY) in egg lecithin/cholesterol liposomes was attempted. IgY was successfully encapsulated into the liposomes by using the dehydration-rehydration method. Electron microscopic observation demonstrated that the liposomes prepared by this method were large multilamellar vesicles with a diameter of several μm. The encapsulation efficiency was improved by increasing the rehydration temperature to 60°C. The cholesterol/lecithin ratio also affected the efficiency, giving the highest value at a ratio of 1/4 (mol/mol). Some efflux of glucose through the liposomal membranes was observed, particularly for the liposome with a low cholesterol content, but that of IgY was not detected, irrespective of the cholesterol content. Encapsulation reduced the activity loss of the IgY antibodies under acidic conditions. IgY encapsulated in the liposomes was also markedly resistant to pepsin hydrolysis, which usually results in complete loss of activity with unencapsu...

Encapsulation of chicken egg yolk immunoglobulin G (IgY) by liposomes.

Effect of sugars on the stabilization of hen egg yolk immunoglobulin (IgY) under various processing conditions was investigated. By adding 30–50% (w/v) sucrose or invert sugar to an IgY solution heat denaturation of the IgY antibody at 75–80°C was markedly suppressed. A high concentration of sugar was also effective to retain the IgY activity under acidic conditions of pH 3 or high pressure of 5,000 kg/cm2 at 60°C. Addition of high concentrations of sucrose may be a simple means to stabilize IgY for processing and preservation.

Egg Yolk Antibody (Ig Y) Stability in Aqueous Solution with High Sugar Concentrations

1. 1. Molecular stability of immunoglobulin G (IgG) from chicken and four mammalian species (cow, goat, pig and rabbit) was compared from immunochemical and biochemical view-points. 2. 2. IgG from cow, goat and pig showed similar stability against denaturation caused by heat, acid and denaturant treatments, while rabbit IgG was shown to be more resistant to all of the treatments than other mammalian IgGs, suggesting that rabbit IgG has a highly stable molecular structure. 3. 3. The heat- and acid-stability of chicken IgG measured by immunochemical methods were similar to those of cow, goat and pig IgG. Conformational stability of chicken IgG measured by fluorometric and enzymatic methods, however, was lower than the mammalian IgGs, suggesting that chicken IgG has a more flexible and unstable molecular structure.

Comparative studies on molecular stability of immunoglobulin G from different species

The Effect of vegetable extracts on intestinal epithelial permeability was investigated by using Caco-2 cell monolayers as the model system. Among 32 kinds of vegetable samples, the extract of sweet pepper is considered to have contained certain substances that could modulate the tight junction permeability.

Kei Hashimoto

Papers

Molecular Stability of Chicken and Rabbit Immunoglobulin G

Encapsulation of chicken egg yolk immunoglobulin G (IgY) by liposomes.

Egg Yolk Antibody (Ig Y) Stability in Aqueous Solution with High Sugar Concentrations

Comparative studies on molecular stability of immunoglobulin G from different species

Effect of Vegetable Extracts on the Transepithelial Permeability of the Human Intestinal Caco-2 Cell Monolayer