OBJECTIVETo investigate the quantity, subset of dendritic cells (DC) and their costimulatory molecule expression in peripheral blood (PB) of the patients with myelodysplastic syndromes (MDS).

METHODSTotal DC (Lin1(+) HLA-DR(+)), myeloid DC (mDC) (Lin1(-) HLA-DR(+) CD11c(+)) and plasma DC (pDC) (Lin1(-) HLA-DR(+) CD123(+)) in fresh PB samples of 38 MDS patients and 19 normal controls were assayed by flow cytometry with the monoclonal antibodies. The expressions of costimulatory molecules CD80, CD86 and CD40 on these DCs were also assayed in the same way.

RESULTSThe number of total DC in PB of low-risk and high-risk MDS patients was significantly higher than that in normal controls [(33.7 +/- 7.0) x 10(6)/L, (56.3 +/- 29.0) x 10(6)/L vs (12.1 +/- 1.4) x 10(6)/L, respectively] (P < 0.05), that of mDC in PB of low-risk and high-risk MDS patients was higher than that of normal controls too [(16.7 +/- 6.3) x 10(6)/L, (28.7 +/- 17.6) x 10(6)/L vs (5.5 +/- 0.9) x 10(6)/L] (P < 0.05), but pDC in low-risk and high-risk MDS patients was not significantly higher than that in normal controls (P > 0.05). The percentage of total DC in PB mononuclear cells (PBMNC) of low-risk and high-risk MDS patients [(2.37 +/- 0.53)% and (3.58 +/- 1.39)% respectively and that of mDC (0.90 +/- 0.35)%, (1.51 +/- 0.70)% respectively] were higher than that of normal controls [(0.68 +/- 0.08)%, and (0.32 +/- 0.05)% respectively] (P < 0.05), but that of pDC in MDS cases was not higher than that of normal controls (P > 0.05). The expressions of CD80 and CD86 between MDS patients and normal controls had significant difference (P < 0.05).

CONCLUSIONSTotal DC and mDC were increased significantly in MDS, but pDC did not. The costimulatory molecules (CD80 and CD86) except CD40 expressed higher on the DC of MDS patients. It suggested that the inflammatory injury related APC increased in MDS, but the antitumour immunity related APC did not . What found here might be one of the mechanisms involved in the pathogenesis of MDS.