Evaluation of the luciferase assay-based in vitro elicitation test for serum IgE.
BACKGROUND
An in vitro elicitation test employing human high-affinity IgE receptor-expressing rat mast cell lines appears to be a useful method for measuring mast cell activation using a patient's IgE and an allergen; however, such cell lines are sensitive to human complements in the serum. We have recently developed a new luciferase-reporting mast cell line (RS-ATL8) to detect IgE crosslinking-induced luciferase expression (EXiLE) with relatively low quantities of serum IgE.


METHODS
A total of 30 patients suspected of having egg white (EW) allergy were subjected to an oral food challenge (OFC) test; then, the performances of EW-specific serum IgE (CAP-FEIA), EW-induced degranulation, and EXiLE responses in RS-ATL8 cells were compared using receiver-operating characteristic (ROC) curve analysis. The patients' sera were diluted to 1 : 100, which causes no cytotoxicity when sensitizing the RS-ATL8 cells for the degranulation and EXiLE tests.


RESULTS
The area under the ROC curves was highest in the EXiLE test (0.977), followed by CAP-FEIA (0.926) and degranulation (0.810). At an optimal cutoff range (1.648-1.876) calculated from the ROC curve of the EXiLE test, sensitivity and specificity were 0.944 and 0.917, respectively. A 95% positive predictive value was given at a cutoff level of 2.054 (fold increase in luciferase expression) by logistic regression analysis.


CONCLUSIONS
In contrast to in vivo tests, the EXiLE test appears to be a useful tool in diagnosing patients suspected of having IgE-dependent EW allergy without the risk of severe systemic reactions.
Division of Novel Foods and Immunochemistry, National Institute of Health Sciences, 1−18−1 Kamiyoga, Setagaya-ku, Tokyo, Japan.ryosnak@nihs.go.jp
Ryosuke
R
Nakamura
Ayano
A
Ishiwatari
Masakazu
M
Higuchi
Yoshimi
Y
Uchida
Rika
R
Nakamura
Hiroshi
H
Kawakami
Atsuo
A
Urisu
Reiko
R
Teshima
D000293:Adolescent; D000328:Adult; D000485:Allergens / Q000276:immunology*; D000818:Animals; D000918:Antibody Specificity / Q000276:immunology; D015550:Cell Degranulation; D002460:Cell Line; D002648:Child; D002675:Child, Preschool; D021181:Egg Hypersensitivity / Q000175:diagnosis* / Q000276:immunology*; D004529:Egg White / Q000009:adverse effects*; D005260:Female; D006801:Humans; D007124:Immunoenzyme Techniques; D007073:Immunoglobulin E / Q000097:blood* / Q000276:immunology; D008156:Luciferases; D008163:Luminescent Measurements; D008297:Male; D008407:Mast Cells / Q000276:immunology / Q000378:metabolism; D012372:ROC Curve; D051381:Rats; D012680:Sensitivity and Specificity; D055815:Young Adult
D000485:Allergens; D007073:Immunoglobulin E; D008156:Luciferases