Changes of CD4 ＋CD25highFoxp3 ＋regulatory T cells and their significance in childhood B-cell acute lymphocytic leukemia

Abstract

Objective To investigate the changes of CD4 ＋CD25highFoxp3 ＋regulatory T （Treg） cells and their significance in immune escape of childhood B-cell acute lymphocytic leukemia （ B-ALL ） . Methods Forty-two children with B-ALL and twenty-eight age-matched healthy children were enrolled in this study.Flow cytometry analysis was performed to evaluate the proportion of CD 4 ＋CD25high Foxp3 ＋Treg cells as well as CD4 ＋CD25high ICOS＋Foxp3 ＋and CD4 ＋CD25high ICOS-Foxp3 ＋subsets in peripheral blood samples.The expression of associated molecules including IL-10, TGF-β, IL-35, TGF-βRII, ICOS and CD28 at protein level were also measured by flow cytometry analysis .The transcription level of Smad3/4, TIEG1 and Itch by CD4 ＋T cells were determined by quantitative real-time PCR.The concentration of TGF-βin plasma was detected by enzyme-linked immunosorbent assay.Results （1）The proportion of CD4 ＋CD25highFoxp3 ＋Treg cells in children with B-ALL were significantly higher than those of health subjects （P〈0.05）.The proportion of both ICOS ＋Foxp3 ＋and ICOS -Foxp3 ＋subsets were increased in comparison with those of control group （P〈0.05）, while the ratio of ICOS ＋Foxp3 ＋to ICOS-Foxp3 ＋was decreased （0.73 ±0.21 vs 1.87 ±0.59, P〈0.05）.（2） The expression of Foxp3, TGF-β, IL-10 and IL-35 by ICOS＋Foxp3 ＋Treg cells and the expression of membrane bound TGF-βby ICOS -Foxp3 ＋Treg cells were significantly increased in children with B-ALL （P〈0.05）.However, the expression of Foxp3 by ICOS -Foxp3 ＋Treg cells showed no significant difference between the two groups （P〉0.05）.（3）The concentra-tion of TGF-βin plasma from children with B-ALL were higher than those from control group [ （ 25 .83 ±12.65） ng/ml vs （8.59 ±5.73） ng/ml, P〈0.05].The expression of TGF-βRII and its associated mole-cules （Smad3/4, TIEG1 and Itch） by CD4 ＋T cells were significantly up-regulated.Moreover, an increased expression of ICOS and CD28 by CD4 ＋CD25highFoxp3 ＋Treg cells were also observed in children with B-ALL （P〈0.05）.Conclusion The hyper-activity of TGF-β, ICOS and CD28 signaling might be closely associ-ated with the increased proportion of CD4 ＋CD25high Foxp3 ＋Treg cells and the imbalance of its subsets in children with B-ALL. Key words: B-cell acute lymphoblastic leukemia; Regulatory T cells; Foxp3; ICOS; CD28