Evidence for cell-mediated hypersensitivity as an important pathogenetic mechanism in food intolerance

PPARgamma Deficiency Counteracts Thymic Senescence

Thymic senescence contributes to increased incidence of infection, cancer and autoimmunity at senior ages. This process manifests as adipose involution. As with other adipose tissues, thymic adipose involution is also controlled by PPARgamma. This is supported by observations reporting that systemic PPARgamma activation accelerates thymic adipose involution. Therefore, we hypothesized that decreased PPARgamma activity could prevent thymic adipose involution, although it may trigger metabolic adverse effects. We have confirmed that both human and murine thymic sections show marked staining for PPARgamma at senior ages. We have also tested the thymic lobes of PPARgamma haplo-insufficient and null mice. Supporting our working hypothesis both adult PPARgamma haplo-insufficient and null mice show delayed thymic senescence by thymus histology, thymocyte mouse T-cell recombination excision circle qPCR and peripheral blood naive T-cell ratio by flow-cytometry. Delayed senescence showed dose-response with respect to PPARgamma deficiency. Functional immune parameters were also evaluated at senior ages in PPARgamma haplo-insufficient mice (null mice do not reach senior ages due to metabolic adverse affects). As expected, sustained and elevated T-cell production conferred oral tolerance and enhanced vaccination efficiency in senior PPARgamma haplo-insufficient, but not in senior wild-type littermates according to ELISA IgG measurements. Of note, humans also show increased oral intolerance issues and decreased protection by vaccines at senior ages. Moreover, PPARgamma haplo-insufficiency also exists in human known as a rare disease (FPLD3) causing metabolic adverse effects, similar to the mouse. When compared to age- and metabolic disorder-matched other patient samples (FPLD2 not affecting PPARgamma activity), FPLD3 patients showed increased human Trec (hTrec) values by qPCR (within healthy human range) suggesting delayed thymic senescence, in accordance with mouse results and supporting our working hypothesis. In summary, our experiments prove that systemic decrease of PPARgamma activity prevents thymic senescence, albeit with metabolic drawbacks. However, thymic tissue-specific PPARgamma antagonism would likely solve the issue.

Protective effect of Enterococcus faecalis DAPTO 512 on the intestinal tract and gut mucosa: milk allergy application

The allergenicity of β-lactoglobulin (β-Lg) was studied by using Ussing chamber in a murine model of β-Lg allergy supplemented with hydrolysates obtained after fermentation of milk for 48 h at 37 (°)C with Enterococcus faecalis DAPTO 512, isolated from cow milk and identified by 16S rDNA sequence analysis. Balb/c mice were sensitised intraperitoneally with β-Lg. Three groups of mice were formed: group 1, composed of naive mice used as control received only NaCl; group 2, positive control composed of mice sensitised intraperitoneally with β-Lg; group 3, formed by mice which were given hydrolysates of 48 h then sensitised with β-Lg. After 48 h of fermentation β-casein and β-Lg were degraded by E. faecalis DAPTO 512. β-Lg immunisation was associated with strong IgG and IgE production in case of positive controls and a significant increase in short current circuit (Isc) and high conductance (G) responses were observed. The control and the hydrolysate groups showed a significant decrease in the production of IgG and IgE anti β-Lg compared to the positive control. The allergenic potential of β-Lg was markedly reduced in the group that received hydrolysates (Isc and G remained unchanged after intestine challenge with β-Lg). The histological scrutiny showed villi atrophy, lymphocyte hyperplasia and a significant chorion detachment in the positive control group. In the group administered with hydrolysates of fermented milk, inflammatory signs were lower, the villi were long and thin and lymphocytes were less dense. The results showed that feeding of milk fermented with E. faecalis DAPTO 512 during 18 days prior to β-Lg allergy induction exerts a protecting effect on the murine intestine and induces a significant decrease in the β-Lg allergenicity.

Effect of heat denaturation on beta-lactoglobulin-induced gastrointestinal sensitization in rats: denatured betaLG induces a more intensive local immunologic response than native betaLG

Beta-lactoglobulin (betaLG) is one of the first foreign antigens encountered by a newborn child, and it is the major allergen causing cow's milk allergy. Heat denaturation causes changes to the protein structure, but the significance of heat-induced changes for immunogenicity or allergenicity is not known. To clarify how heat denaturation affects allergenicity and immunogenicity, we immunized Hooded-Lister rat pups with intra-peritoneal injections of native or heat-denatured betaLG at days 43 and 62 after birth. The animals were then fed native and denatured milk products twice weekly from 73 to 101 days of age with a feeding tube, after which they were allowed cheese and milk ad libitum, until they were killed on day 131. Total immunoglobulin (Ig)E and betaLG-specific IgG1 and IgG2a levels were determined from serum samples. Spontaneous interleukin-4 (IL-4) and interferon-gamma (IFN-gamma) production was measured from duodenal specimens, and specimens of gastrointestinal mucosae were studied for the presence of inflammatory cells. The rats immunized with native betaLG had higher levels of total serum IgE than the unimmunized controls or the rats immunized with heat-denatured betaLG, while heat-denatured betaLG induced a significantly more intensive mononuclear inflammatory cell and eosinophil infiltration in the gastroduodenal mucosa. The betaLG-specific IgG antibody and IL-4 and IFN-gamma responses were similar in the two groups of immunized animals. Hence, denaturation modifies the immunogenic and allergenic properties of betaLG. Heat-denatured betaLG induces a more intensive local reaction in the gastrointestinal mucosa, while there is some evidence for enhanced systemic allergic sensitization by native betaLG.

A similar high level of immunoglobulin A and immunoglobulin G class milk antibodies and increment of local lymphoid tissue on the duodenal mucosa in subjects with cow's milk allergy and recurrent abdominal pains

In previous studies, we have reported endoscopic and histological alterations locally on the gastrointestinal (GI) tract associated with a gastrointestinal type of cow's milk allergy. In this study, we sought to further characterize endoscopic, and immunological findings in these children. We also hypothesized that the same type of immune responses might also be found in children with unexplained and recurrent abdominal pains. We did a gastroduodenoscopy for persistent GI symptoms, examined the mucosal histology of the small intestine and measured the antibodies to whole cow's milk and its fractions with an enzyme-linked immunosorbent assay (ELISA) in a consecutive series of 22 subjects with untreated and 14 with treated cow's milk allergy (CMA) and 44 with recurrent abdominal pains (RAP). The immunological findings of the study subjects were compared with 54 controls. Lymphonodular hyperplasia (LNH) of the duodenum was the main endoscopic finding in 11 subjects (50%) with untreated and 5 (36%) with treated CMA. It was also found in 6 of 44 subjects with RAP. Compared with the controls, the patients with CMA showed significantly higher levels of IgA class antibodies to whole milk (p = 0.003) and betaLG (p < 0.0001). Of the IgG class antibodies to betaLG (p = 0.032), BSA (p < 0.0001) and alphaCAS (p < 0.0001) were significantly higher. The patients with LNH of the duodenal bulb as the main endoscopic finding showed significantly higher values of IgG class antibodies to betaLG (p = 0.01) and alphaCAS (p = 0.005). Interestingly, the patients examined for RAP showed a similar increment in the pattern of whole milk and specific milk protein antibodies as the CMA children. In conclusion this study showed that gastrointestinal CMA beyond infancy is significantly associated with high levels of IgG and IgA class antibodies to milk and its fractions. As high levels of these antibodies and LNH of the duodenal bulb were also found in subjects with RAP, the study further suggests that gastrointestinal CMA might be one major reason for RAP.

Children with untreated food allergy express a relative increment in the density of duodenal gammadelta+ T cells

BACKGROUND

We investigated whether children with food allergy (FA) express increased densities of intraepithelial gammadelta+ T cells similarly to subjects with celiac disease.

METHODS

The duodenal specimens taken by gastroduodenoscopy from 20 children with untreated FA, 17 with treated FA, 12 with celiac disease (CD) and 12 controls were studied with monoclonal antibodies and a three-layer peroxidase staining method.

RESULTS

The subjects with untreated FA expressed equal densities of total intraepithelial CD3+ and alpha/beta+ T cells, but significantly higher densities of gammadelta+ cells than the subjects currently on an elimination diet for FA or the controls. Accordingly, their gammadelta+/CD3+ ratio was higher. On the other hand, the results differed clearly from CD, where all the three cell populations showed high densities. Another finding that discriminated the subjects with FA from the CD patients was endoscopic examination. Lymphonodular hyperplasia (LNH) of the duodenal bulb with a normal villous pattern was demonstrated in 14 (70%) of the 20 subjects with untreated FA and in 8 (47%) of the 17 with treated FA, but in none of the celiac patients or controls. Surprisingly, the biopsy samples from the subjects with FA showed quite normal histological findings.

CONCLUSIONS

According to this preliminary observation, high densities of intraepithelial gammadelta+ T cells and a significantly elevated gammadelta+/CD3+ ratio are associated with untreated FA. If seen LNH in a gastroduodenoscopy and/or increased densities of gammadelta+ T cells in the biopsy specimen, the possibility of gastrointestinal FA should be reliably assessed by a food challenge.