A. Hoffmann et al., BIOLOGIC ALLERGEN ASSAY FOR IN-VIVO TEST ALLERGENS WITH AN IN-VITRO MODEL OF THE MURINE TYPE-I REACTION, Journal of allergy and clinical immunology, 99(2), 1997, pp. 227-232
Background: The determination of the biologic activity of allergenic e
xtracts in human beings is limited for ethical and practical reasons.
The establishment of a simplified in vitro model, which mimics a main
event of the type I reaction, should provide true benefit for manufact
urers, researchers, and clinicians. Objective: This study was designed
to develop and evaluate a mediator release assay based on rat basophi
l leukemia cells for the purpose of investigating allergenic extracts.
Methods: Rat basophil leukemia cells were passively sensitized with m
urine IgE raised against allergens and stimulated by serial dilutions
of allergenic extracts in a dose-related manner. The allergen-specific
degranulation was monitored by measuring the release of beta-hexosami
nidase. Results: The investigation of standardized commercial allergen
products for in vivo diagnostics (birch pollen, cat dander, and bee v
enom) allowed a quantitative description of differences in biologic ac
tivity in accordance with the declared activity units. The Fel d 1 con
tent was determined in 17 cat dander extracts and correlated well with
the results of a two-site binding ELISA (r = 0.93, log/log). Extremel
y low allergen amounts in the range of 10 to 100 pg/ml could be easily
detected. Moreover, the cross-reactivity pattern of patients allergic
to birch pollen could be reproduced with extracts of hazel, alder, ap
ple, and celery. Conclusion: The assay is suitable for supplementing q
uality control of allergenic extracts and for the determination of bio
logic activity of final allergen products. As a research tool, it allo
ws the study of IgE cross-linking properties of modified and recombina
nt allergens at an early stage before they are tested in human beings.