Objective To investigate the effect of iuvenile rheumatoid arthritis(JRA) serum (leukotriene B4,LTB4) LTB4-BLT2 on mice DCs.Methods Bone marrow(BM)-derived DCs from healthy mouse were purified.and induced by cytokine IL-4 and GM-CSF to immature DCs and then differentiated to mature DCs under the stimulation of LPS in vitro.DCs were evaluated by light microscope and flow cvtometry.The concentrations of LTB4 in DCs supernatant,normal serum,active JRA,and that of the co-cuItured with BLT2 antagonist LY255283 were detected by ELISA.The expression of BLT2 protein and mRNA in DCs was examined by immunocytochemistry,immunofluorescence and RT-PCR.Meanwhile,the expression of BLT2 in DCs after 18 h co-cultured with normal serum,in serum of active JRA and that of BLT2 antagonist (LY255283)group was assayed by flow cytometry respectively.Results LTB4-BLT2 was expressed by DCs.Not only BLT2 mRNA but also its protein was expressed in DCs.The concentration of LTB4 Was(17±3)pg/ml,(82±20)pg/ml,(82±20)pg/ml and(24±6)pg/ml,(115±20)pg/ml,(91±11)pg/ml in normal serum group,active JRA group and LY255283 group before and after 1 8 h,respectively.The expression Was higher in serum of active JRA group than that of normal sertlm group(P<0.01)and there was a tendency to be higher when compared with LY255283 group(P<0.05).The DC BLT2 expression was 27.7±2.9,46.3±8.7 and 30.3±5.5 in normal serum group,serum of active JRA group and LY255283 grbup after 1 8h respectively.The expression was stronger in active JRA group than other groups(P<0.05).Conclusion DC can develop a LTB4-BLT2 signal pathway by BLT2 with autocrine and/or extrinsic LTB4.The overexpression of this pathway may be involved in the initiating and activation of JRA.