['The aim of our study was to estimate the expressions of both B7-H1 and B7-H4 as well as CD200 and CD200R co-stimulatory molecules on immature myeloid and lymphoid dendritic cells, B CD19(+)  lymphocytes and monocytes in umbilical cord blood of healthy neonates and in peripheral blood of healthy adults.', "Thirty-nine healthy full-term neonates from physiological single pregnancies and 27 healthy adults were included in the study. The expressions of B7-H1, B7-H4, CD200, CD200R antigens were estimated using flow cytometry. Statistical analysis was performed using a non-parametric Mann-Whitney U-test and parametric Wilcoxon's test.", 'The expressions of B7-H1 and B7-H4 molecules on immature BDCA-1(+)  myeloid dendritic cells were significantly lower in umbilical cord blood of healthy neonates when compared with those cells in peripheral blood of healthy adults (P\xa0<\xa00.0001). Furthermore, the suppression of B7-H4 molecule on BDCA-2(+)  lymphoid dendritic cells was observed in cord blood of healthy neonates when compared with peripheral blood of healthy adults (P\xa0<\xa00.02). The expressions of CD200 antigen on BDCA-1(+)  cells, CD200R antigen on BDCA-2(+)  cells and CD200R antigen on B CD19(+)  cells were significantly lower in cord blood of healthy neonates. On the other hand, the expressions of CD200 and CD200R as well as B7-H4 co-stimulatory molecules on CD14(+)  cells were significantly higher in cord blood when compared with peripheral blood.'] Are the expressions of co-stimulatory molecules altered on putative antigen-presenting cells in cord blood?