OBJECTIVETo study the changes of IL-12 produced by dendritic cells in peripheral blood in children with Henoch-Schonlein purpura (HSP), and to explore its influence on TH1/TH2 balance in order to elucidate its significance in the pathogenesis of HSP.

METHODSThe levels of interferon-gamma (IFN-gamma), interleukin-4 (IL-4) and interleukin-12 (IL-12) in plasma were determined by ELISA in 60 HSP children (HSP group) and 21 healthy children (Control group). Peripheral blood mononuclear cells (PBMC) of 22 HSP patients and 21 healthy children were cultured in vitro and then were transformed into dendritic cells. The levels of IL-12 in the supernatant were detected by ELISA and the positive expression rate of CD1a(+) was detected by indirect immunofluorescence procedure.

RESULTS1) The levels of IFN-gamma and the ratio of IFN-gamma/IL-4 in plasma of the HSP group were lower than those of the Control group (IFN-gamma 30.59 +/- 11.27 pg/mL vs 43.38 +/- 19.19 pg/mL; IFN-gamma/IL-4 ratio 0.70 +/- 0.28 vs 1.33 +/- 0.57) (P < 0.01). The levels of IL-12 in the HSP group were also lower than those of the Control group (153.95 +/- 91.88 pg/mL vs 323.06 +/- 162.34 pg/mL; P < 0.01). In contrast, the levels of IL-4 were higher than those of the Control group (45.08 +/- 9.19 pg/mL vs 32.95 +/- 7.10 pg/mL; P < 0.01). The plasma levels of IL-12 positively correlated with the IFN-gamma levels (r=0.52, P < 0.01) and the ratio of IFN-gamma/IL-4 (r=0.43, P < 0.01) in the HSP group. 2) The IL-12 levels in the supernatant of the HSP group were lower than those of the Control group (357.06 +/- 153.56 pg/mL vs 489.80 +/- 213.45 pg/mL; P < 0.05), and had a positive correlation with the plasma IL-12 levels (r=0.74, P < 0.01). 3) The positive expression rate of CD1a(+) of the HSP group was lower than that of the Control group [(27.42 +/- 10.75)% vs (35.68 +/- 12.18)%; P < 0.05], and positively correlated with the IL-12 levels in the supernatants (r=0.57, P < 0.01) and in plasma (r=0.68, P < 0.01).

CONCLUSIONSThere was an imbalance of TH1/TH2 in HSP children. The decrease of TH1 function had a positive correlation with the low levels of IL-12 in plasma, while the latter correlated closely with decreased number and / or function of dendritic cells, suggesting that the decreased number and / or function of dendritic cells in peripheral blood resulted in the imbalance of TH1/TH2 indirectly.