METHODS: PBMCs were isolated from controls and subjects with alpha-gal allergy and stained for surface markers CD19, CD38, CD27, CD138, and membrane IgM, IgG, IgD and IgE as well as fluorochrome-labeled alpha-gal.
RESULTS: IgE+B cells that also stained positive for alpha-gal were identified in five subjects allergic to mammalian meat. These alpha-gal-specific IgE+B cells were absent in controls. Of total stained singlet cells, the population of alpha-gal-specific IgE+B cells was 0.092% (median) with a range of 0.013% to 0.15%. There was no association of alpha-gal-specific IgE+B cell frequency with reported severity of allergic reactions. Interestingly, subjects reporting ongoing consumption of alpha-gal antigen in dairy form had generally higher proportion of antigen-specific IgE+B cells.
CONCLUSIONS: We have reproducibly identified circulating antigen-specific IgE+B cells in adult subjects with alpha-gal mammalian meat food allergy. Although BCR signaling is thought to negatively regulate IgE responses, our data suggest ongoing dietary antigen exposure is associated with increased numbers of antigen-specific IgE+B cells. Future studies will track these double-positive B cells longitudinally to assess the impact of additional tick bites.