Proliferative responses of CD4+ T-cell population to ovalbumin in patients with atopic dermatitis who are sensitive to hen eggs

Novel B and T cell epitopes of chicken ovomucoid (Gal d 1) induce T cell secretion of IL-6, IL-13, and IFN-gamma

BACKGROUND

Chicken ovomucoid (OM, Gal d 1) has an important role in the pathogenesis of IgE-mediated allergic reactions to hen's egg white.

OBJECTIVES

The purpose of this study was to clarify the mechanisms of T cell recognition of ovomucoid using intact OM and chemically modified, characterized and homogeneous solid phase synthetic peptides covering the whole molecule.

METHODS

Eighteen overlapping peptides were prepared by solid phase F-moc polyamide peptide synthesis (SPPS), characterized and high-pressure liquid chromatography (HPLC) purified. The peptides, together with intact, denatured and oxidized OM, were used to stimulate patient-derived cell cultures for mapping T cell epitopes. Proliferation responses, T cell phenotype and cytokine secretion using peripheral blood mononuclear cells (PBMC) from eight individuals and T cell lines (TCL) derived from six hen's egg-allergic patients, were examined. In addition, intact, denatured, oxidized and deglycosylated OM, as well as the peptides solely or with their keyhole limpet haemocyanin (KLH) complexes, were tested. For locating IgE and IgG B cell epitopes, seven egg-allergic patient sera and three OM-polyclonal sera were used. Healthy non-allergic individuals were included as controls.

RESULTS

Seven peptides were recognized by specific IgE, while OM-specific TCL recognized 10 peptides. Six of the OM peptides were commonly recognized both by patient S-IgE and blood-derived TCL. Among those, one novel epitope, peptide OM 61-74, had the ability to bind IgE. Another peptide, OM 101-114, was recognized by IgE and IgG sera, but not by any of the TCLs. In contrast, the peptides OM 41-56, OM 71-84, OM 131-144 and OM 171-186 were exclusively T cell epitopes with no affinity to specific antibodies. Abundant TCL secretion of IFN-gamma, IL-6, IL-4, IL-13, IL-10 and TNF-alpha in response to OM stimulation indicates the contribution of Th2 as well as Th1/Th0 CD4+ cell subsets. For allergic patients moderate amounts of IFN-gamma, IL-13, and high amounts of IL-6, were secreted in response to TCL stimulation by OM peptides. High amounts of IL-6 were secreted in response to all molecular forms of OM (intact-, modified-OM and the peptides 71-84 and 51-64) when TCLs from two non-allergic donors were used.

CONCLUSIONS

One novel B cell epitope (OM 61-74) and 10 T cell epitopes have been identified. The most reactive epitopes of the OM molecule comprise the motifs 1-14 to 71-84, the overlapping peptide-pairs OM 121-134 and OM 131-144 and peptides OM 161-174 and 171-186. Peptides OM 1-14 and 171-186 are the only ones capable of inducing IL-4 secretion. Only one peptide (OM 11-24) induces IL-10 secretion. Those peptides recognized as both T and B cell epitopes or only T cell epitopes, have the potential to induce T cell secretion of moderate to high amounts of IL-13, IFN-gamma and particularly IL-6.

Milk-responsive atopic dermatitis is associated with a casein-specific lymphocyte response in adolescent and adult patients

BACKGROUND

Specific T-cell responses to food antigens have been described in children with atopic dermatitis (AD). However, a subgroup of adolescent and adult patients still experiences food-responsive AD.

OBJECTIVE

This study was designed to evaluate lymphocyte responses to bovine casein in adult patients with AD.

METHODS

The stimulatory capacity of lipopolysaccharide-depleted bovine casein was tested in proliferation assays and in limiting dilution assays. Casein-specific T-cell clones (TCCs) were generated and characterized.

RESULTS

Higher proliferative responses to casein and modulation of cytokine receptors were observed in patients with milk-responsive AD compared with individuals without clinical reactions on milk ingestion. The results did not correlate with the amount of casein-specific IgE in the serum. The frequencies of T cells that grew in the presence of casein or house dust mite antigens were similar. Only 27% of CD4+ casein-specific TCCs from these patients, but the majority of house dust mite-specific TCCs, produced IL-4 on mitogen stimulation. Interferon-gamma, on the other hand, was produced by the majority of TCCs with both specificities.

CONCLUSION

A specific T-cell-mediated immune response to casein can be found in the blood of adolescent and adult patients with milk-related exacerbation of AD. In contrast to house dust mite-specific T cells, casein-specific T cells of adult patients who respond to cow's milk with worsening of AD produce little or no IL-4.

Inhibition of interferon-gamma and interleukin-2 production from lymphocytes stimulated with food antigens by an anti-allergic drug, Tranilast, in patients with food-sensitive atopic dermatitis

N(3',4'-dimethoxycinnamoyl) anthranilic acid (Tranilast) inhibits antibody-mediated hypersensitivity reactions, and is an effective drug for patients with bronchial asthma or allergic rhinitis. Interferon-gamma (IFN-gamma) production of ovalbumin (OA)-stimulated peripheral blood mononuclear cells (PBMCs) from hen's egg-sensitive patients with atopic dermatitis (AD) was significantly higher than those of healthy controls. Tranilast inhibited this IFN-gamma production. Moreover, interleukin-2 (IL-2) production of OA-stimulated PBMCs from hen's egg-sensitive patients with AD was also inhibited by Tranilast. Our results suggest that Tranilast can be used to the patients with food sensitive AD.

Suppressive effects of elimination diets on T cell responses to ovalbumin in hen's egg-sensitive atopic dermatitis patients

We investigated the effect of elimination diets on T cell responses to ovalbumin (OA) in hen's egg-sensitive atopic dermatitis (AD) patients. The proliferative responses of both peripheral blood mononuclear cells (PBMCs) and T cells with monocytes to OA decreased after elimination diets, but those to Candida albicans or phytohemagglutinin (PHA) did not decrease after elimination diets. The proliferative responses of CD4+ T cells with monocytes to OA decreased after elimination diets. In these patients, clinical symptoms of AD improved. These results indicate that T cells, especially CD4+ T cells, respond to food antigens in food-specific lymphocyte responses, and that elimination diets may be able to initiate reduction of the responsiveness of food-sensitive T cells, especially CD4+ T cells. Moreover, the surface marker phenotypes of the T cells responding to OA were analysed. Our results showed that CD4+CD45RA+ T cells tended to increase. The increase in circulating CD4+CD45RA+ T cells might function as systemic suppression against immune responses in the skin.