OBJECTIVETo study the role of Th17/Treg imbalance in the immune pathogenesis and therapeutic significance in childhood aplastic anemia (AA).

METHODWe analyzed data from 43 children (male: female = 14: 29) with AA, all the cases were at the age of 2 to 14 years at diagnosis, and were hospitalized at our department of pediatrics between January 2012 and October 2013 in the Second Hospital of Anhui Medical University. All these patients were divided into 2 groups, severe AA (SAA) group (n = 25, male: female = 8: 17, 2-14 years old) and non-severe AA (NSAA) group (n = 18, male: female = 6: 12, 2-14 years old), depending on the severity at first diagnosis. As to the treatment, we analyzed data at 3 phases of treatment, diagnosis (n = 43, male: female = 14: 29, 2-14 years old), transfusion-indenpendence (n = 8, male: female = 5: 3, 2-11 years old), complete response (n = 6, male: female = 3: 3, 2-11 years old); at the same time, AA children who did not respond to the treatments were considered as failed treatment control (transfusion-indenpendence with failed treatment group, n = 5, male: female = 1: 4, 3-8 years old; complete response failed treatment group, n = 4, male: female = 2: 2, 4-11 years old). The ratio of Treg and Th17 cells in CD4(+) T cells were tested by flow cytometry. The levels of IL-6 and IL-17 in plasma were determined by ELISA. During the same period, 25 age-matched healthy children (male: female = 12: 13, 3-14 years old) were recruited as normal control, 9 cases (male: female = 5: 3, 2-11 years old) of AA children induced by chemotherapy as diagnosis control group. Differences in variables were analyzed using ANOVA and t-tests or the Kruskal-Wallis and Mann-Whitney U-tests, as appropriate. Correlation analysis was evaluated by the Spearman rank correlation test.

RESULT(1) The ratio of Th17 cells in newly diagnosed AA patients were higher than that of normal group or diagnosis control group [1.63% (1.27%, 2.48%) vs. 0.4% (0.35%, 0.51%) or 0.50% (0.45%, 0.75%), both P < 0.01] while the ratio of Treg cells was lower [4.24% (3.10%, 5.29%) vs. 7.03% (6.56%, 7.48%) or 7.50% (6.60%, 8.30%), both P < 0.01] and the proportion of Th17/Treg were significantly higher [0.53(0.34, 0.69) vs. 0.06 (0.05, 0.07) or 0.09 (0.08,0.11), both P < 0.01]. (2) The levels of IL-6 and IL-17 in newly diagnosed AA patients were higher than in normal group [ (223 ± 92) vs. (116 ± 18) ng/L, (26.2 ± 12.0) ng/L vs. (10.6 ± 2.1) ng/L, P both < 0.01]. There was a positive correlation between Th17 cells and some Th17 cells related cytokines such as IL-17 and IL-6 (r = 0.62, 0.64, P both < 0.01). (3) The ratio of Th17, Th17/Treg, and the levels of IL-6 and IL-17 in children with SAA were also higher than in normal group [1.80% (1.25%, 2.61%) vs. 0.40% (0.35%, 0.51%), 0.57% (5.10%,0.82%) vs. 0.06% (0.05%, 0.07%), (225 ± 108) vs. (116 ± 18) ng/L, (25.9 ± 12.6) vs. (10.6 ± 2.1)ng/L, all P < 0.01]. NSAA also higher than normal group. The ratio of Treg in children with SAA and NSAA was less than that in normal group (P all < 0.01). However, the ratio of Th17, Treg, Th17/Treg, and the levels of IL-6 and IL-17 had no significant difference between SAA and NSAA (all P > 0.05). (4) In different stages of treatment, such as diagnosis, transfusion-indenpendence, complete response, there were significant differences in the ratio of Th17 and Th17/Treg (both P < 0.05) but not in Treg (P > 0.05).

CONCLUSIONThe imbalance of Th17/Treg cells and abnormally increased cytokines related to Th17 cells exist in peripheral blood of AA children, but did not significantly affect the severity of AA in preliminary diagnosis. After treatment with immunosuppression, AA was gradually relieved as the imbalance of Th17/Treg was corrected.