Quantification of specific IgE to whole peanut extract and peanut components in prediction of peanut allergy.

University of Manchester, Manchester Academic Health Science Centre, NIHR Translational Research Facility in Respiratory Medicine, University Hospital of South Manchester NHS Foundation Trust, Manchester, United Kingdom.
The Journal of allergy and clinical immunology (Impact Factor: 12.05). 01/2011; 127(3):684-5. DOI: 10.1016/j.jaci.2010.12.012
Source: PubMed
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    ABSTRACT:   Allergen-specific IgE antibodies are implicated in allergic diseases while allergen-specific IgG antibodies have been proposed to prevent allergic reactions. The objective for this study was to study whether the immune response (IgG and IgG4) to peanut differs in IgE-sensitized and non-sensitized young children.   A total of 239 children have been followed prospectively from birth to 5 yr of age. The levels of IgG and IgG4 to peanut, Ara h 2, and Ara h 8 were analyzed at 2 and 5 yr of age and related to IgE sensitization and peanut consumption.   The levels of peanut-specific IgG and IgG4 were significantly higher in peanut-sensitized children at 2 and 5 yr of age when compared with non-sensitized children and children sensitized to other food/inhalant allergens. A strong correlation was seen between levels of peanut-specific IgG/IgG4-ratios and peanut-specific IgE at 5 yr of age. Children avoiding peanuts, a subgroup of the peanut sensitized, had statistically significant higher levels of IgE to peanut and a tendency of higher IgG and IgG4 levels to peanut. In the avoidance group, significant correlations between IgE and IgG/IgG4 to peanut were found compared with children eating peanuts.   Peanut-specific IgG or IgG4 levels were elevated in peanut-sensitized children especially those avoiding peanuts. In our study, IgG and IgG4 do not seem to indicate tolerance or protection from sensitization.
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    ABSTRACT: Isolated Ara h 8 sensitization is suggested to be associated with no or mild symptoms among peanut-sensitized subjects. We sought to investigate the occurrence of systemic reactions in children with isolated sensitization to Ara h 8. Participants were 144 children sensitized to Ara h 8 (≥ 0.35 kU(A)/L) but not to Ara h 1, Ara h 2, or Ara h 3 (<0.35 kU(A)/L). An open oral challenge with peanut was performed in those subjects who did not consume peanut regularly, and an extended IgE reactivity profile was obtained. If the child had a documented history of systemic reactions up to grade I anaphylaxis, double-blind, placebo-controlled food challenges were performed. One hundred twenty-nine (89.5%) children were either peanut consumers or did not react to peanut challenge. Another 14 (9.7%) children experienced oral cavity symptoms at the first 2 but not subsequent challenge doses. At the time of the double-blind, placebo-controlled food challenge, 1 boy with a previous mild systemic reaction to peanut experienced lip swelling, stomach cramping, and objective tiredness. Reanalysis of IgE levels showed an increase in peanut IgE levels from 1.5 to 8.8 kU(A)/L, but IgE levels to Ara h 8 remained stable and IgE levels to Ara h 1, Ara h 2, and Ara h 3 were all still less than 0.35 kU(A)/L. The IgE level to Ara h 6 was 0.45 kU(A)/L. Isolated Ara h 8 sensitization indicates tolerance to peanuts in almost all cases. However, sensitization against thus far unidentified determinants in peanut might cause symptoms in rare cases.
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