T cell proliferation and cytokine responses to ovalbumin and ovomucoid detected in children with and without egg allergy


Szun Szun Tay, Department of Medicine, Addenbrookes Hospital, Cambridge University, Box 157, Cambridge CB2 2QQ, UK.
E-mail: szunszuntay@hotmail.com


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.