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Background Allergy can be diagnosed using basophil tests. Several methods measuring basophil activation are available. This study aimed at comparing basophil activation test ( BAT), histamine release assay ( HR), and passive sensitization histamine release assay (passive HR) in the diagnosis of peanut allergy. Methods BAT, HR, and passive HR were performed on 11 peanut-allergic and 14 nonallergic subjects. Blood was incubated with peanut extract or anti-IgE and tests were performed as follows: BAT- CD63 upregulation was assessed by flow cytometry; HR-released histamine was quantified by a glass fiber-based fluorometric method; passive HR-IgE-stripped donor basophils were incubated with participants' serum and histamine release was quantified as HR. Results CDsens, a measure of basophil allergen sensitivity, was significantly higher for BAT (80.1±17.4) compared to HR (23.4±10.31) and passive HR (11.1±2.0). BAT, HR, and passive HR had a clinical sensitivity of 100%, 100%, and 82% and specificity of 100%, 100%, and 100%, respectively, when excluding inconclusive results. BAT identified 11 of 11 allergic patients, HR 10, and passive HR 9. Likewise, BAT recognized 12 of 14 nonallergic subjects, HR 10, and passive HR 13. However, the tests' diagnostic performances were not statistically different. Interestingly, nonreleasers in HR but not in BAT had lower basophil count compared to releasers (249 vs 630 counts/min). Conclusion BAT displayed a significantly higher CDsens compared to HR and passive HR. The basophil tests' diagnostic performances were not significantly different. Still, BAT could diagnose subjects with low basophil number in contrast to HR. [ABSTRACT FROM AUTHOR]

Background: Immunoglobulin (Ig)E-sensitized persons with positive skin prick test, but no allergy symptoms, are classified as being asymptomatic skin sensitized (AS). The allergic type 1 disease is dependant on IgE binding to the high affinity IgE-receptor (Fc ℇRI) expressed on basophils and mast cells. However, a relationship between the AS status and Fc ℇRI has not been investigated. We aimed to characterize basophils from AS by looking at histamine release (HR) (sensitivity and reactivity) and the Fc ℇRI molecule, and compare it with nonatopic (NA) or allergic (A) persons. Methods: Blood was obtained from NA ( n = 14), grass and/or birch A persons ( n = 17) and mono-sensitized grass or birch pollen AS ( n = 12). The basophil sensitivity and reactivity were examined by anti-IgE triggered HR. Surface expression of Fc ℇRI and IgE were measured by flow cytometry, Fc ℇRI α protein was identified using a radioimmunoassay and Western blot. mRNA coding for the classic Fc ℇRI β-chain and the truncated form (Fc ℇRI βT) were determined by real-time PCR. Results: The AS group was less reactive than NA or A persons when triggered by anti-IgE and had a significant higher number of nonresponders. However, there was no difference in sensitivity among the three groups and furthermore; the groups did not vary in Fc ℇRI- and IgE-surface expression, Fc ℇRI α-protein level or β/ βT ratio. Conclusion: Basophils from AS persons are less reactive and include more nonresponders than basophils from NA and A persons, but do not differ regarding the Fc ℇRI molecule. [ABSTRACT FROM AUTHOR]

Summary Background The high affinity IgE receptor (FcεRI) on mast cells and basophils is up-regulated by its own ligand IgE; however, the mechanism is unknown. Objective To study the IgE-mediated effect on FcεRI on basophils by using the human basophilic cell line KU812. Methods Expression of cell surface FcεRI was assessed by flow cytometry. Western blot technique was used to illustrate tyrosine-phosphorylation and the Ca2+ level in KU812 was measured by fluorescence of Fura-2. Soluble specimens of the α-chain from FcεRI (FcεRIα) were obtained by lysing 107 KU812 pr. mL. FcεRIα was detected by a sandwich immunoradiometric assay employing the IgE-binding capacity of FcεRIα in conjunction with a monoclonal antibody. Polyclonal rabbit anti-FcεRIα was used for detection of FcεRIα by Western blotting. Results We found that monomeric IgE did not induce tyrosine-phosphorylation in KU812, which was the case when stimulating with IgE cross-linked by anti-IgE binding. Further, only cross-linking of IgE, but not monomeric IgE, increased the Ca2+ level. Using the immunoradiometric assay, we found a temperature dependent reduction in the amount of FcεRIα. Samples incubated at 37 °C for 5 h displayed a 16-fold decrease in the FcεRIα level compared with samples incubated at 4 °C. In the presence of IgE the reduction at 37°C was only threefold. Conclusion These results indicate that IgE does not induce intracellular signals in KU812, i.e., tyrosine-phosphorylation or Ca2+ release. Instead it appears that FcεRIα is an unstable protein that IgE stabilizes and thereby protects from a temperature dependent turnover. [ABSTRACT FROM AUTHOR]