Clinical & Experimental Allergy

Contribution of Ara h 2 to peanut-specific, immunoglobulin E-mediated, cell activation

Authors

  • R. A. McDermott,

    1. Division of Allergy and Clinical Immunology, University of Colorado at Denver and Health Sciences Center, Denver, CO, USA
    2. National Jewish Medical and Research Center, Denver, CO, USA
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  • H. S. Porterfield,

    1. Division of Allergy and Clinical Immunology, University of Colorado at Denver and Health Sciences Center, Denver, CO, USA
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  • R. El Mezayen,

    1. Division of Allergy and Clinical Immunology, University of Colorado at Denver and Health Sciences Center, Denver, CO, USA
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  • A. W. Burks,

    1. Duke University, Durham, NC, USA
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  • L. Pons,

    1. Duke University, Durham, NC, USA
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  • D. G. Schlichting,

    1. Division of Allergy and Clinical Immunology, University of Colorado at Denver and Health Sciences Center, Denver, CO, USA
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  • B. Solomon,

    1. Proteomics Shared Resource, University of Colorado Cancer Center, University of Colorado at Denver and Health Sciences Center, Denver, CO, USA
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    • 1Current address: Peter MacCallum Cancer Centre St Andrews Place East, Melbourne, Vic. 3002, Australia

  • J. S. Redzic,

    1. Proteomics Shared Resource, University of Colorado Cancer Center, University of Colorado at Denver and Health Sciences Center, Denver, CO, USA
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  • R. J. Harbeck,

    1. National Jewish Medical and Research Center, Denver, CO, USA
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  • M. W. Duncan,

    1. Proteomics Shared Resource, University of Colorado Cancer Center, University of Colorado at Denver and Health Sciences Center, Denver, CO, USA
    2. Department of Pediatrics, School of Medicine, University of Colorado at Denver and Health Science Center, Denver, CO, USA
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  • K. C. Hansen,

    1. Proteomics Shared Resource, University of Colorado Cancer Center, University of Colorado at Denver and Health Sciences Center, Denver, CO, USA
    2. Department of Pediatrics, School of Medicine, University of Colorado at Denver and Health Science Center, Denver, CO, USA
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  • S. C. Dreskin

    1. Division of Allergy and Clinical Immunology, University of Colorado at Denver and Health Sciences Center, Denver, CO, USA
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Correspondence:
Stephen C. Dreskin, Division of Allergy and Clinical Immunology, University of Colorado Health Sciences Center, Campus Box B164, 4200 E. Ninth Ave. Denver, CO 80262, USA.
E-mail: stephen.dreskin@uchsc.edu

Summary

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 ∼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.

Conclusion 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.

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