Peanut-allergic subjects and their peanut-tolerant siblings have large differences in peanut-specific IgG that are independent of HLA class II.

We enrolled 53 peanut-allergic subjects and 64 peanut-tolerant full siblings, measured peanut-specific IgG and IgE, determined HLA class II at high resolution, and analyzed DRB1 alleles by supertypes. Peanut-specific IgG and IgE were elevated in the peanut-allergic subjects (p<0.0001) but did not stratify with HLA alleles, haplotypes, or supertypes. There were no significant differences in HLA class II between the peanut-allergic and peanut-tolerant siblings but there was an increased frequency of DRB1*0803 in both sets of siblings compared to unrelated controls (p(c)=4.5×10⁻9). Furthermore, we identified 14 sibling pairs in which the peanut-allergic and the peanut-tolerant siblings have identical HLA class II and again found an elevation of anti-peanut IgG in the peanut-allergic subjects (p<0.0001). In conclusion, although DRB1*0803 may identify a subset of families with increased risk of peanut allergy, differences in peanut-specific immunoglobulin production between peanut-allergic subjects and their peanut-tolerant siblings are independent of HLA class II.