Abstract: Background: The diagnosis of allergic diseases lacks definite test criteria and mainly depends on the clinical history. In the absence of allergen stimulation, there are no clinical symptoms, making the diagnosis more difficult. Therefore, it is very important to find auxiliary diagnostic markers for allergic diseases. Objective: Detection of lymphocyte subsets in allergic children is expected to provide a new marker for the diagnosis of allergic diseases. Design: Casecontrol study. Methods: Children with food allergy and respiratory allergy were selected as the allergic disease group, and healthy children matching with gender and age in the same period were selected as the control group. Lymphocyte subsets was analyzed by flow cytometry. Main outcome measures: Lymphocyte subsets. Results: The average age of 30 patients in the allergy group was 3.6 (0.710.6) years, and that of 27 healthy controls was 4.1 (0.811) years. There was no significant difference in age and gender between the two groups (P value was 0.616 and 0.574). For T lymphocyte subsets, the ratio of Th2 cells/effectors helper T cells and Th2/Th1 ratio in the allergic disease group were higher than those in the healthy control group ［(31.34±2.52)% vs (20.02±2.05)%, (6.86±1.51) vs (2.73±0.35)］, and the differences were statistically significant. Percentage and absolute count of mature B cells, absolute count of plasmablasts, percentage of IgE+ plasmablasts, percentage of IgE+ memory B cells in allergic children were higher than those of healthy controls ［(11.53 ± 1.22) % vs (6.02±0.52)%, (1,068±107.3) cells per μL vs (578.74±58.49)cells per μL , (40.71±6.44) cells per μL vs (17.08±2.93)cells per μL , (8.21±1.33) % vs (1.64±0.53)%, (4.48±0.81) % vs (0.47±0.18)%］. Conclusion: The increased percentage of Th2 cells, IgE+ plasmablasts and memory B cells in allergic children may be a marker for the diagnosis of allergy.

Key words: Allergy, Th1/Th2, B cell, Plasmablast, IgE