Brown Norway rat ovalbumin-specific immunoglobulin E antibodies increase the human basophil expression of CD63 marker.

Anaphylactic shock is an immunoglobulin E (IgE)-dependent hypersensitivity. Biological tests like leucocyte histamine release (LHR) and human basophil activation (HBA), frequently used in human allergy, reflect both the amount of IgE fixed on cells and the cellular reactivity. To assess whether serum-specific IgE from Brown Norway (BN) rats prepared for ovalbumin (OVA)-induced anaphylactic shocks can activate human basophils which has a potential interest in experimental allergy: such a test could rapidly assert an IgE sensitization in laboratory animals genetically T-helper 2 (Th2)-predisposed. Rats (n = 39) were immunized three times (day 0, day 5 and day 21) with OVA injected subcutaneously. One week after the third immunization, a shock was induced with an intravenous (i.v.) bolus of OVA. Sensitization was assessed by passive cutaneous anaphylaxis (PCA) test and dosages of serum IgE antibodies anti-OVA by enzyme-linked immunosorbent assay. Blood basophils were counted before and during the shock. Before the shock induction (at day 21), an LHR test was performed on rat blood, and human basophils were sensitized with rat sera. HBA was demonstrated by the increase in the percentage of cells expressing CD63 antigen membrane, measured by flow cytometry. Twenty-one days after the first subcutaneous (s.c.) immunization, the rat serum induced a significant HBA. HBA was observed neither with the same serum previously heated nor with the serum from nonimmunized rats (NIRs). OVA-specific IgEs were significantly increased in immunized rat (IR) serum. The PCA test was negative when the serum was previously heated (56 degrees C). We never observed any circulating basophils, and LHR test was negative. After OVA i.v. administration, all IRs died rapidly. HBA testing strongly suggests a mediation by specific IgE in the increase of CD63 in BN rats. Thus, HBA test seems useful in assessing whether an experimental allergy was induced in animals genetically predisposed to an immune response, Th2-mediated, like BN rat. We also conclude that rat basophil activation does not participate in the histamine release during anaphylactic shock in sensitized BN rats.

Identification and partial characterization of multiple major allergens in peanut proteins.

BACKGROUND: Peanuts are a major cause of food allergies both in children as in adults which can induce an anaphylactic shock. The identification and characterization of peanut allergens could lead to more insight into the mechanism and contribute to the improvement of diagnostic tests and treatment for peanut allergy. OBJECTIVE: In the present study, the peanut protein-specific immunoglobulin concentrations as well as their recognition of the various peanut proteins or protein subunits was determined in the plasma of peanut-allergic (PA) and non-allergic (NA) individuals. Moreover, two peanut allergens were characterized in more detail to confirm them as the earlier described Ara h1 and Ara h2. METHODS: The presence of Ig-binding sites in peanut proteins was studied by immunoblotting assays whereas the concentrations of peanut-specific Ig was determined by ELISA. RESULTS: Peanut proteins were found to contain multiple binding sites for immunoglobulins. Of these proteins, six were recognized by peanut-specific IgE present in more than 50% of the plasma samples of the PA group. Their molecular weights were approximately 44, 40, 33, 21, 20 and 18 kDa. The last three protein bands were recognized by peanut-specific IgE present in more than 70% of the PA plasma samples and were thought to contain Ara h2. This allergen as well as another protein that was thought to be Ara h1, which was not recognized by the majority of the patients' IgE-containing plasma samples, were isolated and the N terminal amino acid sequence was determined. Peanut protein-specific IgA, IgM, IgG and IgG-subclasses showed a more diverse recognition pattern of peanut protein in the PA group compared to the NA group. No differences were found in the plasma concentrations of peanut protein-specific immunoglobulins of the various classes between the PA and NA group. CONCLUSIONS: From the present study, we conclude that peanuts contain multiple allergens, of which six can be described as major allergens, Ara h2 included. In our population Ara h1 is not a major allergen. The recognition of peanut proteins by immunoglobulins is more diverse in PA individuals compared with NA individuals which, however, is not substantiated in the concentrations of peanut-specific immunoglobulins in plasma, other than IgE.

A new method to measure iron absorption from the enrichment of 57Fe and 58Fe in young erythroid cells.

Iron absorption can be measured by the incorporation of stable iron isotopes into erythrocytes, 14 days after isotope administration. The disadvantage of this method is the high dose of isotopes needed to obtain a sufficient enrichment. Therefore, in this study cell fractions rich in young erythroid cells were prepared by using a density separation method. From 10 women blood was taken 4, 5, and 7 days after oral and intravenous administration of 57Fe and 58Fe. In these cell fractions and in whole blood taken 14 days after isotope administration, isotope enrichment was measured and absorption calculated. Absorption calculated from the isotope enrichment in the reticulocyte-rich cell fractions (12.2 +/- SEM 3.7%) was not significantly different from absorption based on whole-blood values (13.0 +/- 3.3%). Because a threefold higher isotope enrichment was found in the cell fractions, the required dose of stable isotopes can be reduced to one-third of the dose used in the traditional method without loss of sensitivity.