[Function of CD4(+) CD25(+) regulatory T cells in Henoch-Schonlein purpura nephritis in children].

OBJECTIVE: To investigate the levels and functions of CD4(+)CD25(+) regulatory T cells and specific transcription factor Foxp3 and Th17 cells related cytokine in peripheral blood mononuclear cells (PBMC) and renal tissues, and explore their roles in pathogenesis of Henoch-Schonlein purpura nephropathy (HSPN) in children.

METHOD: From March, 2011 to March, 2013, 30 cases of HSPN children underwent renal biopsy and were treated in Guiyang Children's Hospital were enrolled into this study. Ten healthy children who underwent health check up were enrolled as blood sample control group. The normal kidney tissue specimens were taken from 5 children who underwent surgery for urologic disorders were used as renal sample control group. The circulating proportions of CD4(+)CD25(+) regulatory T cells in PBMC of 30 cases of HSPN children and 10 cases of control group were determined by flow cytometry, respectively.Reverse transcription-polymerase chain reaction (RT-PCR) were used to analyze the mRNA expressions of IL-17, IL-1β and Foxp3 in PBMC. The expression of IL-17 and IL-1β in renal tissue of HSPN and control group were measured by immunohistochemistry. CD4(+)CD25(+) regulatory T cells, Foxp3, IL-17, IL-1β expression were analyzed and compared in HSPN group and control groups respectively.

RESULT: Thirty cases of HSPN pathological classification were as follows: type I was found in 0 case; type II in 9 cases; type III in 16 cases; type IV in 5 cases; type V in 0 case. The circulating proportions of CD4(+)CD25(+)/CD4(+)T cells and the CD4(+)CD25(+)Foxp3(+)Treg/CD4(+)T cells level were (5.84 ± 0.78)%, (1.01 ± 0.46) % in HSPN groups were substantially lower than those in control group. All these two differences had statistical significance (t = 27.200, 33.260, P < 0.05). The mRNA levels of IL-17, IL-1β in HSPN groups (0.86 ± 0.01,0.71 ± 0.01) were higher than those in control group (t = 25.000, 31.840, all P < 0.05). Foxp3 mRNA expression in HSPN groups (0.24 ± 0.02) were significantly lower than those in control group (t = 21.690, P < 0.05). Protein expression of IL-17 and IL-1β in renal tissues of HSPN children (13.31 ± 0.54, 11.56 ± 0.28) were significantly stronger than those in the control group (t = 27.6, 14.0, all P < 0.01). The highest level of protein expression of IL-17 and IL-1β in renal biopsy of HSPN was in type IV (IV>III>II, F = 545.800, 262.500, all P < 0.01).

CONCLUSION: The disorder of quantity and function of CD4(+)CD25(+) regulatory T cells, and increase in levels of IL-17, IL-1β (cytokine related to Th17 cells) may play important roles in pathogenesis of HSPN in children; increased protein expression of IL-17, IL-1β in renal tissue may contribute to the development of renal pathological damage in HSPN children.