OBJECTIVETo investigate the influence of low doses of granulocyte macrophage colony stimulating factor on the allogeneic antigen (Ag) ingestion capacity of immature dendritic cells (GM low DC), and subsequently the changes in the cellular phenotype and function.

METHODSMononuclear cells from C57BL/6 mice was labelled with 3H-Leu to make Ag supernatant. The Ag supernatant was cocultured with GM low DC or mature DC for 30,60 and 90 mins, then cpm value were determined. The changes in I(A)/I(E) and CD80 on cell surface after antigen ingestion were determined with flow cytometry (FCM). By using mixed lymphocyte reaction (MLR), the cells were divided into control (non-sensitized T lymphocyte), GM low DC, GM low DC and allogeneic antigen, GM low DC and allogeneic antigen and CTLA-4 Ig groups. The cpm value in each group was recorded and the stimulation index (SI) was calculated.

RESULTSUpon 30, 60 and 90 mins of allogeneic Ag stimulation, the cpm value of GM low DC was obviously higher than that of mature DC (P < 0.05 or 0.01). In addition, the expression of I(A)/I(E) and CD80 before allogeneic Ag ingestion were significantly higher than those after Ag ingestion (I(A)/I(E): 32 +/- 8% vs. 54 +/- 10, P < 0.05; CD80: 25 +/- 10% vs. 71 +/- 18%, P < 0.01). MLR: Compared with control group, the cpm value in GM low DC with allogeneic Ag group was increased markedly (P < 0.05), with SI higher than 2.0, while no difference was found among control, GM low DC group, GM low DC and allogeneic Ag and CTLA-4Ig groups (P > 0.05), with SI lower than 2.0

CONCLUSIONThough GM low DC exhibits powerful antigen ingestion capacity, the cell phenotype and function will get mature gradually. Immune tolerance can be established by incubating GM low DC with CTLA-4Ig.