Contribution of Ara h 2 to peanut-specific, immunoglobulin E-mediated, cell activation.
BACKGROUND
Ara h 2 is a potent peanut allergen but its contribution to the ability of a crude peanut extract (CPE) to cross-link IgE and activate mast cells has not been rigorously evaluated.


OBJECTIVE
To measure the contribution that Ara h 2 makes to the effector function of a CPE.


METHODS
Ara h 2 was specifically removed from a CPE as demonstrated by immunoblots, 2D gels, and an inhibitory ELISA. Functional assays of sham-treated and Ara h 2-depleted CPEs were performed with RBL SX-38 cells sensitized with IgE from highly peanut-allergic subjects and with naturally sensitized basophils.


RESULTS
Depletion of approximately 99% of the Ara h 2 from the CPE led to an increase in the concentration of the CPE necessary to give 50% of maximal degranulation (EC50) of the SX-38 cells following sensitization with sera that contain anti-Ara h 2 IgE. Assays with a pool of 10 sera showed a small but significant increase in the EC50 following depletion of Ara h 2 (1.65+/-0.15-fold; P<0.05) and assays of seven individual sera showed a similar increase in the average EC50 (1.7+/-0.2-fold; P<0.02). The percent of the anti-peanut IgE that binds Ara h 2 correlated with an increase in the EC50 of the CPE following depletion of Ara h 2 (r=0.83; P<0.02). On the other hand, data from three of these patients studied with a basophil histamine release assay did not show a significant effect of depletion of Ara h 2.


CONCLUSIONS
Based on its ability to cross-link IgE effectively, Ara h 2 is clearly an important peanut allergen. Its ability to cross-link IgE effectively from a specific serum is related to the proportion of anti-Ara h 2 in that serum but Ara h 2 does not account for a majority of the effector activity of the CPE for any of the sera studied.
McDermott
R A
RA
Division of Allergy and Clinical Immunology, University of Colorado at Denver and Health Sciences Center, Denver, CO 80262, USA.
Porterfield
H S
HS
El Mezayen
R
R
Burks
A W
AW
Pons
L
L
Schlichting
D G
DG
Solomon
B
B
Redzic
J S
JS
Harbeck
R J
RJ
Duncan
M W
MW
Hansen
K C
KC
Dreskin
S C
SC
D055516:2S Albumins, Plant; D000293:Adolescent; D000328:Adult; D000368:Aged; D000485:Allergens / Q000032:analysis / Q000276:immunology*; D052179:Antigens, Plant; D010367:Arachis / Q000276:immunology*; D015549:Basophil Degranulation Test; D001491:Basophils / Q000276:immunology; D002648:Child; D002675:Child, Preschool; D015180:Electrophoresis, Gel, Two-Dimensional / Q000379:methods; D006023:Glycoproteins / Q000276:immunology*; D006801:Humans; D007073:Immunoglobulin E / Q000097:blood / Q000276:immunology*; D008407:Mast Cells / Q000276:immunology; D008875:Middle Aged; D021183:Peanut Hypersensitivity / Q000276:immunology*; D010936:Plant Extracts / Q000276:immunology; D010940:Plant Proteins / Q000276:immunology*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods
D055516:2S Albumins, Plant; D000485:Allergens; D052179:Antigens, Plant; C500890:Ara h 2 allergen, Arachis hypogaea; D006023:Glycoproteins; D010936:Plant Extracts; D010940:Plant Proteins; D007073:Immunoglobulin E