Summary An enzyme‐linked immunosorbent assay (ELISA) was developed to assess serum IgE antibodies directed against Pityrosporum ovale in patients with atopic dermatitis (AD), atopic patients with allergic respiratory disease (ARD: rhinitis or asthma) but without eczema, and in healthy controls. IgE binding to P.ovale extract was demonstrated in 49% (35/72) of AD patients. In contrast, anti‐P. ovale IgE was found in only one of 27 atopic controls without eczema: all healthy control sera (n=17) were negative. Of 37 AD patients tested intracutaneously with P. ovale. 31 showed immediate‐type reactivity, and 20 of these 31 patients had anti‐P. ovale IgE detectable by ELISA, while sera from the six non‐responders were all negative. Levels of anti‐P. ovale IgE were highest in AD patients aged 20–30 years. No correlation was found with the severity of AD, but there was a non‐significant tendency (P=0.06) to higher levels in AD patients with concomittant respiratory allergy. Anti‐P.ovale IgE was significantly correlated with total serum IgE, with specific IgE against various aeroallergens as measured by RAST, and with levels of anti‐Candida albicans IgE, measured with a similar ELISA. Thus, production of IgE antibodies against P. ovale occurs very frequently in AD, and rarely in patients with atopic disease without skin involvement.

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Background: The role of antigen-specific T cells in the mechanism of food allergy or maintenance of tolerance toward an innocuous antigen, such as cow's milk, is not yet fully understood. Objective: The cow's milk-specific T-cell response of donors with various allergic backgrounds was investigated. Methods: Cow's milk-specific T-cell clones (TCCs) were generated from the blood of children with persistent cow's milk allergy (CMA) and the blood of cow's milk-tolerant allergic and nonallergic control subjects. The TCCs were characterized by their antigen-specific proliferation, cytokine production, and activation status. Results: Cow's milk-specific TCCs of children with persistent CMA were T H 2 skewed, and the production of IL-4 and IL-13 was significantly correlated with the expression of the activation marker CD25. TCCs of the allergic control subjects were characterized by a high production of IL-10, which was positively correlated with the production of IL-4 and IFN-g and with the expression of CD25. TCCs derived from nonallergic control subjects had an attenuated response toward cow's milk in that they did not produce high levels of cytokines nor did they express high levels of surface markers. As in the allergic control subjects, in the nonallergic control subjects IL-10 production was positively correlated with the expression of CD25. Conclusion: The activation status of T cells derived from persistent donors with CMA was associated with the production of IL-4 and IL-13, whereas activated TCCs of cow's milktolerant control subjects were characterized by the production of IL-10 and, to a lesser extent, IFN-g. These findings suggest that activated CD4 + T cells (characterized by a high CD25 expression) might contribute to the tolerogenic immune response toward an antigen, such as cow's milk, through the production of

Background: Previous studies suggest that administration of probiotics in vitro can stimulate regulatory and Th1 immune responses. We studied both the in vitro immunological effects of probiotics and the ex vivo immunological effects after oral administration of probiotics in children with food allergy, a Th2-mediated disease. Methods: Thirteen children were enrolled. Probiotics (n = 7) or placebo (n = 6) were orally administered during 3 months. At baseline and after 1 and 3 months, peripheral blood mononuclear cells were stimulated with crude peanut extract, anti-CD3, or anti-CD40 and IL-4 in the presence (in vitro response) or absence (ex vivo response) of probiotics. The proliferation and production of IFN-γ, IL-5, IL-13, IL-10, TNF-α, IL-6 and IgE were analyzed. Sensitization to peanut, cow’s milk and hen’s egg was determined before and after treatment. Results: The in vitro addition of probiotics to peripheral blood mononuclear cell cultures resulted in enhanced proliferation and production of IFN-γ, IL-10 and TNF-α. After oral treatment, proliferation in the presence of probiotics increased, whereas in vitro IgE production decreased in the probiotics group compared to baseline. The ex vivo production of IL-10, TNF-α and IL-6 tended to decrease. Th1 and Th2 cytokines were not altered. Sensitization remained unchanged. Conclusion: Probiotics enhanced the production of Th1 and regulatory cytokines in vitro. Oral administration of probiotics resulted in a slightly decreased ex vivo production of IL-10, TNF-α and IL-6. This indicates that probiotics have a different potential to modulate the immune response in vitro versus ex vivo.

Preparations obtained from the exponential phase of yeast cultures (2-4 days old), should preferably be used in studies of the IgE response to P. orbiculare.

Pityrosporum ovale has recently been recognized as a source of allergens to which many patients with atopic dermatitis (AD) show type I skin reactions and specific IgE antibodies. In this study the IgE-binding components and/or epitopes in P. ovale extract were shown to be partially sensitive to pronase or trypsin treatment, whereas periodate oxidation resulted in a complete loss of IgE-binding capacity, thus suggesting the involvement of carbohydrate structures. In Con A affinity chromatography most of the IgE-binding capacity of crude P. ovale extract bound to the column, and could be eluted with mannoside. Gel filtration on Sephacryl S-400 revealed a marked heterogeneity with respect to molecular mass, with most of the IgE-binding activity associated with high-mol.-mass fractions (from 5 x 10(4) up to 2 x 10(6) Da). A similar heterogeneity was found after chromatofocusing, with IgE-binding in the whole pI-range from 7.0 to 4.0. Essentially identical results were obtained with extracts of Candida albicans, in agreement with the previously shown cross-reactivity of IgE-binding components in the two yeast extracts. In inhibition ELISA, gel filtration and chromatofocusing fractions containing components with widely different mol. mass or pI showed complete reciprocal cross-inhibition, and were all capable of inhibiting the binding of IgE to unfractionated extracts. We therefore conclude that the cross-reacting anti-P. ovale/anti-C. albicans IgE antibodies in the sera of AD patients are mainly directed at a restricted number of carbohydrate epitopes that are expressed on a heterodisperse range of high-mol.-mass components, probably mannans or mannoproteins.

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