A convenient and sensitive allergy test: IgE crosslinking-induced luciferase expression in cultured mast cells.
BACKGROUND
For the detection of allergen-specific IgE in sera, solid-phase IgE-binding assays like the CAP test are commonly used. Although such immunochemical methods are very sensitive, they frequently produce false positives. Degranulation of the human IgE receptor (FcεRI)-transfected rat mast cell (RBL) lines seems to be a possible indicator for human IgE, but spontaneous mediator release from these cells in the presence of human sera is not negligible.


METHODS
The nuclear factor of activated T-cells (NFAT)-responsive luciferase reporter gene was stably transfected into human FcεRI-expressing RBL-SX38 cells. One established clone (RS-ATL8) was sensitized with 1 : 100 dilution of sera from patients with egg white allergy and then stimulated with purified or a crude extract of egg white allergen.


RESULTS
Sensitization with 15 pg/ml IgE was sufficient to detect IgE crosslinking-induced luciferase expression (EXiLE) by anti-IgE stimulation. Allergen-specific EXiLE was elicited by as little as 1 fg/ml of egg white protein without cytotoxicity. There was a good correlation between results with EXiLE and oral food challenge tests on patients with egg allergy (P = 0.001687, Fisher's exact test). The measured values of EXiLE and the CAP test also correlated well (R = 0.9127, Spearman's test).


CONCLUSIONS
The EXiLE test using RS-ATL8 cells is a promising in vitro IgE test to evaluate the biological activity of the binding between IgE and allergens.
Nakamura
Ryosuke
R
Division of Novel Foods and Immunochemistry, National Institute of Health Science, Setagaya-ku, Tokyo, Japan. ryosnak@nihs.go.jp
Uchida
Y
Y
Higuchi
M
M
Nakamura
R
R
Tsuge
I
I
Urisu
A
A
Teshima
R
R
D000485:Allergens / Q000276:immunology; D000818:Animals; D000888:Antibodies, Anti-Idiotypic; D000937:Antigen-Antibody Reactions; D002478:Cells, Cultured; D021181:Egg Hypersensitivity / Q000175:diagnosis; D004527:Egg Proteins / Q000009:adverse effects / Q000276:immunology; D006801:Humans; D006967:Hypersensitivity / Q000175:diagnosis*; D007073:Immunoglobulin E / Q000276:immunology*; D008156:Luciferases; D008407:Mast Cells / Q000166:cytology / Q000276:immunology*; D051381:Rats
D000485:Allergens; D000888:Antibodies, Anti-Idiotypic; D004527:Egg Proteins; C026408:anti-IgE antibodies; D007073:Immunoglobulin E; D008156:Luciferases