Background The specific T cell responses in egg allergy and resolution have not been fully elucidated.
Objective To characterize egg allergen-specific T cells of children with active and resolved egg allergy, in comparison with non-allergic controls.
Method We studied children with active (n=35) or resolved (n=20) egg allergy determined by oral challenge, and non-allergic controls (n=15). Peripheral blood mononuclear cells were labelled with carboxyfluorescein succinimidyl ester (CFSE) and stimulated with ovalbumin (OVA), ovomucoid (OM) or tetanus toxoid. Flow cytometry was used to detect divided CD3+ CFSElo cells that expressed intra-cytoplasmic IL-4 or IFN-γ. The cell division index (CDI) was calculated as a measure of allergen-specific proliferation. Peanut-specific T cells of a subgroup of children who also had peanut allergy were also studied.
Results OVA-specific T cells were found in subjects with active (87%) or resolved (75%) egg allergy and in controls (67%), with a trend towards increased T cell proliferation in allergy. OM-induced weaker T cell responses than OVA, stimulating fewer responders (46% allergic, 50% resolved, 60% controls) and 10-fold less proliferation [CDIOVA 2.0 (median), 25.6 (maximum) vs. CDIOM 0.2 (median), 15.1 (maximum); P<0.01]. Both egg allergens induced significant IL-4+ (median 10%, range 1.4–58%) and IFN-γ+ (median 28%, range 4.5–63%) cells in responders, including non-allergics. There were no significant differences in IFN-γ+ or IL-4+ cells or in IFN-γ/IL-4 ratios between groups. Peanut-specific T cell proliferation was significantly higher in peanut allergy [CDICPE 16.5 (median), 24.8 (maximum)] compared with controls [CDICPE 2.1 (median), 16.1 (maximum)] but cytokine profiles were not different. Tetanus-specific T cells were seen in 90% of the subjects, with no significant inter-group differences in responses.
Conclusion Egg allergen-specific T cells are readily detected in all groups and not restricted to egg allergy. In contrast, peanut-specific proliferation was significantly higher in peanut allergy. This suggests that T cell responses in peanut and egg allergy may differ. We did not find T helper type 2-deviated cytokine responses in egg or peanut allergy.