Allergen-specific CD8+ T cells in peanut-allergic individuals

To the Editor: CD8+ T cells are uncommonly thought to be involved in IgE-mediated food allergy, but there are reasons to reconsider their role in this condition.1 CD8+ T cells are present in skin, and in the respiratory and gut mucosae, where they may modulate the immune response in atopic conditions such as asthma and atopic dermatitis.2-4 In mice, CD8+ T cells attenuate food allergy in some experimental models, whereas in humans, CD8+ T cells have been shown to expand in response to wheat ingestion in celiac disease.1,5,6 Despite the fact that these findings show that CD8+ T cells can recognize food antigen and participate in TH2 immune responses, we are not aware of any previous evidence demonstrating whether CD8+ T cells are specifically activated by allergen in IgE-mediated food allergy in people. CD107a (LAMP1) is expressed on the cell surface of CD8+ T cells after T-cell receptor (TCR) ligation by a cognate peptide:MHC ligand, and so the detection of CD107a on the surface of CD8+ T-cell clones by flow cytometry indicates antigen recognition via the TCR.9 In the case of subjects I and III, we recovered CD8+ T-cell clones that mobilized CD107a after incubation with the same pool of peanut-derived peptides initially used to activate these cells and isolate them by fluorescence-activated cell sorting (Fig 2, B). Characteristic Subjects in Fig 1, A, and Fig 2 Subjects in Fig 1, B and C Pediatric peanut allergic Adult peanut allergic Peanut allergic Peanut tolerant N 53 21 16 16 Age (y), GM (range) 10.5 (8-18) 29.7 (19-53) 7.45 (5-12) 6.20 (4-13) Sex 20F:33M 5F:16M 7F:9M 8F:8M Peanut IgE (kUA/L), GM (range) 54.3 (0.41-869) 15.6 (0.62-221) 177.2 (13-676) NA Peanut allergy All (+) by FC All (+) by FC All (+) by FC None by hx ± IgE History of atopic dermatitis, n (%) 40 (75) 11 (52) 8 (50) 0 (0) History of asthma, n (%) 36 (68) 17 (81) 11 (69) 0 (0) Race/ethnicity 32W:16A:0B:5O 13W:5A:1B:2O 5W:10A:1B:0O 9W:4A:1B:2O Table I Patients' demographic characteristics