Peanut Specific IgG4 and its Association with Peanut Allergy

Abstract

RATIONALE: Approximately 50% of children with measurable specific IgE to peanut are allergic and reactive to peanut. The remaining 50% are able to eat peanut without a reaction. Distinguishing between the clinically allergic and sensitized individuals may be difficult. We explore the role of peanut specific IgG4 in distinguishing between children who are clinically allergic and sensitized to peanut. METHODS: Clinical evaluation included; history, examination, skin prick testing, and oral challenge testing to peanut. Specific IgE and IgG4 to peanut were performed using Pharmacia Immuno CAP-RAST in 91 children attending a London based paediatric allergy clinic. All patients had eczema. Patients were considered peanut allergic (PA) if they had a positive specific IgE and reacted to peanut, and peanut sensitized (PS) if specific IgE positive but peanut tolerant. RESULTS: Thus far, 35 patients have proven peanut allergy and 20 patients have been shown to be clinically tolerant. The remaining patients have an indeterminate status and are awaiting peanut challenge. Median peanut specific IgE was 7.17 (3.1-40.3) kU/L in the PA patients compared to 4.36 (1.25-9.04) kU/L in the PS patients (p=0.046). Median specific IgG4 in allergic and sensitized patients was 239 (1.5-1062) ug/ml and 625.5 (87.75-1895) ug/ml respectively (p=0.1921). Median specific IgG4/IgE results showed values of 14.8 (0.7-57.6) in the PA patients vs. 142.8 (7.3-364.0) in PS patients (p=0.0170). CONCLUSIONS: This data suggests that specific IgG4 determination may have a role in distinguishing between peanut allergic and peanut sensitized patients.